Features of CDMA The following features are unique to CDMA technology: Universal frequency reuse Fast and accurate power control Rake receiver Different types of handoff

Frequency reuse The frequency spectrum is a limited resource. Therefore, wireless telephony, like radio, must reuse frequency assignments. For example, two radio stations might transmit at 91.3 FM. There is no interference as long as the radio stations are far enough apart.

FDMA and TDMA frequency reuse planning A frequency (channel) can be used again within an FDMA or TDMA network, but cells using the same frequency must be separated by an appropriate distance. Adjacent cells must be assigned a different set of frequencies. For example, a cell using frequency A must not be adjacent to another cell using frequency A. As a result, each cell site in the site is able to use only 1/7 of the possible frequencies.

CDMA frequency reuse planning Each BTS in a CDMA network can use all available frequencies. Adjacent cells can transmit at the same frequency because users are separated by code channels, not frequency channels. This feature of CDMA, called "frequency reuse of one," eliminates the need for frequency planning.

Power control Power control is a CDMA feature that enables mobiles to adjust the power at which they transmit. This ensures that the base station receives all signals at the appropriate power. The CDMA network independently controls the power at which each mobile transmits. Both forward and reverse links use power control techniques.

Why power control is needed

If all mobiles transmitted at the same power level, the base station would receive unnecessarily strong signals from mobiles nearby and extremely weak signals from mobiles that are far away. This would reduce the capacity of the system. This problem is called the near-far problem.

Rake Receiver The rake receiver is a CDMA feature that turns what is a problem in other technologies into an advantage for CDMA.

How the rake receiver works

CDMA's rake receiver is multiple receivers in one. The rake receiver identifies the three strongest multi-path signals and combines them to produce one very strong signal. The rake receiver therefore uses multipath to reduce the power the transmitter must send. Both the mobile and the BTS use rake receivers.

handoff in CDMA Handoff is the process of transferring a call from one cell to another. This is necessary to continue the call as the phone travels. CDMA is unique in how it handles handoff.

Types of CDMA handoff

CDMA has three primary types of handoff: hard soft idle

The type of handoff depends on the handoff situation.

Types of CDMA handoff CDMA has three primary types of handoff: hard soft idle

The type of handoff depends on the handoff situation.

Soft handoff

A soft handoff establishes a connection with the new BTS prior to breaking the connection with the old one. This is possible because CDMA cells use the same frequency and because the mobile uses a rake receiver. The CDMA mobile assists the network in the handoff. The mobile detects a new pilot as it travels to the next coverage area. The new base station then establishes a connection with the mobile. This new communication link is established while the mobile maintains the link with the old BTS. Soft handoffs are also called "make-before-break."

Soft handoff in action

Variations of the soft handoff There are two variations of soft handoffs involving handoffs between sectors within a BTS: Softer Soft-softer

The softer handoff occurs between two sectors of the same BTS. The BTS decodes and combines the voice signal from each sector and forwards the combined voice frame to the BSC. The soft-softer handoff is combination handoff involving multiple cells and multiple sectors within one of the cells.

CDMA hard handoff A hard handoff requires the mobile to break the connection with the old BTS prior to making the connection with the new one. CDMA phones use a hard handoff when moving from a CDMA system to an analog system because soft handoffs are not possible in analog systems. A Pilot Beacon Unit (PBU) at the analog cell site alerts the phone that it is reaching the edge of CDMA coverage. The phone switches from digital to analog mode as during the hard handoff. Hard handoffs are also called "break-before-make."

When does CDMA use a hard handoff? The CDMA hard handoff may be used when moving from a CDMA network to an analog one. It may also be used when moving to a different: RF channel MTSO Carrier Market

Analog to CDMA handoff is not available due to the limitations of analog technology.

CDMA idle handoff An idle handoff occurs when the phone is in idle mode. The mobile will detect a pilot signal that is stronger than the current pilot. The mobile is always searching for the pilots from any neighboring BTS. When it finds a stronger signal, the mobile simply begins attending to the new pilot. An idle handoff occurs without any assistance from the BTS.

Advantages of CDMA CDMA technology has numerous advantages including: Coverage Capacity Clarity Cost Compatibility Customer satisfaction

Coverage CDMA's features result in coverage that is between 1.7 and 3 times that of TDMA: Power control helps the network dynamically expand the coverage area. Coding and interleaving provide the ability to cover a larger area for the same amount of available power used in other systems.

Capacity CDMA capacity is ten to twenty times that of analog systems, and it's up to four times that of TDMA. Reasons for this include: CDMA's universal frequency reuse CDMA users are separated by codes, not frequencies Power control minimizes interference, resulting in maximized capacity.

CDMA's soft handoff also helps increase capacity. This is because a soft handoff requires less power.

Clarity Often CDMA systems can achieve "wireline" clarity because of CDMA's strong digital processing. Specifically: The rake receiver reduces errors The variable rate vocoder reduces the amount of data transmitted per person, reducing interference. The soft handoff also reduces power requirements and interference. Power control reduces errors by keeping power at an optimal level. CDMA's wide band signal reduces fading. Encoding and interleaving reduce errors that result from fading.

Cost CDMA's better coverage and capacity result in cost benefits: Increased coverage per BTS means fewer are needed to cover a given area. This reduces infrastructure costs for the providers. Increased capacity increases the service provider's revenue potential.

CDMA costs per subscriber has steadily declined since 1995 for both cellular and PCS applications.

Compatibility CDMA phones are usually dual mode. This means they can work in both CDMA systems and analog cellular systems. Some CDMA phones are dual band as well as dual mode. They can work in CDMA mode in the PCS band, CDMA mode in the cellular band, or analog mode in an analog cellular network.

Customer satisfaction CDMA results in greater customer satisfaction because CDMA provides better: Voice quality Longer battery life due to reduced power requirements No cross-talk because of CDMA's unique coding Privacy--again, because of coding.

CDMA: stands for Code Division Multiple Access. Both data and voice are separated from signals using codes and then transmited using a wide frequency range. Because of this, there are more space left for data transfer (this was one of the reasons why CDMA is the prefered technology for the 3G generation, which is broadband access and the use of big multimedia messages). 14% of the worldwide market goes to CDMA. For the 3G generation CDMA uses 1x EV-DO and EV-DV. It has a lot of users in Asia, specially in South Korea. GSM: stands for Global System Mobile. Even though it is sold as "the latest technology" in several countries, this technology is older than CDMA (and also TDMA). But keep in mind that this doesn't mean that GSM is inferior or worse than CDMA. Roaming readiness and fraud prevention are two major advantages from this technology. GSM is the most used cell phone technology in the world, with 73% of the worldwide market. It has a very strong presence in Europe.

TDMA technology is the less used from the three main digital technologies (GSM, CDMA and TDMA) and we think it will gradually be replaced to CDMA or GSM. That's why the GSM vs CDMA war. At one corner, GSM operators say it is better "because it uses a SIM chip, it is the most used technology worldwide, it is more secure and it is more advanced". On the other corner, CDMA followers say it is better "because it is the 3G generation chosen technology and GSM will migrate to CDMA since CDMA is more advanced..." But which one of these statements are correct? Acordingly to Nokia, "this discussion is not about technology anymore, but about market". We think this is the best way to describe the war between these two cell phone technologies. In the beginning, GSM was in fact superior. It had more services and allowed more data transfer. But CDMA, facing the advantages of the competitor standard, soon delivered the same features found on GSM. Nowadays, it is not possible to say that GSM services are better than CDMA. Multimedia messages, video, high-speed Internet access, digital camera and even PDA function are some of the features we can found on both technologies. The new CDMA 1XRTT technology, which previews what G3 cell phones will bring, is more advanced than EDGE, technology from the beginning of 3G generation, allowing higher transfer rates. Even the GSM SIM card advantage, that allows you to change your cell phone and keep your phone list, is being surplaced by some CDMA operators with a service that allows you to store your phone book on the operator's database, allowing you to recover your phone book even if your cell phone is stolen (which is not possible with GSM, since if your cell phone is stolen, your SIM card will be stolen together). Notice that recently a new accessory called SIM backup was released, which allows you to backup the data stored in your SIM card. Also some GSM operators are offering a similar backup service. So, nowadays both technologies are equiparated in technology, but this picture won't be like that in the future. Afterall, CDMA evolution ground is wider and in a few years it will be superior than GSM. This means that GSM operators will disapear? Not at all. They will migrate over CDMA and the war will continue, because the existing CDMA operators chose to use 1xEV-DO and1XEV-DV technologies for their 3G network and the existing GSM operators have opted for a different technology, called WCDMA. Also, even though the current GSM operators will migrate to WCDMA, they still can use their existing GSM network. So users won't feel anything special when the operators shift to the new cell generation (3G), independently from the technology they choose.

In this module you learned about CDMA features such as: Universal frequency reuse Power control Rake receiver Different types of handoff

You also learned how these features provide advantages such as: Coverage Capacity Clarity Cost Compatibility Customer satisfaction

Features of cdma n spread spectrum---http://www.wb.nic.in/nicnet/cband1.html

AMPS: stands for Advanced Mobile Phone Service. Analog cell system. TDMA: stands for Time Division Multiple Access. It works by dividing the spectrum into frequency channels and each user uses each channel for a specific time, to avoid interference. CDMA 1XRTT: Second generation technology (2.5G, actually) which allows data transfers up to 144 Kbps. EDGE: stands for Enhanced Data Rates for Global Evolution. Technology promoted by GSM operators. Before migrating to WCDMA, EDGE will allow third generation data and voice access with 384 kbps transfer rate. EV-DO: Third generation (3G) fromCDMA 1xEV-DO technology. "EV" comes from and "DO" from data-only. It uses a second channel, of 1.25 MHz, exclusively for data transmission. Some countries are already running this standard. In the USA, Verizon and Sprint started this technology in 2004. This tecnology allows hi-speed Internet access (2.4 Mbps) using the cell phone or using a wireless connection from a laptop or PDA. EV-DV: Evolution of EV-DO, but still under development. "DV" comes from dataand-voice. It uses the same channel for trasmiting data and voice. The transfer rate can reach 5.2 Mbps. WCDMA: Wideband CDMA. Third generation technology that will be adopted by GSM operators. Its European version is known as UMTS (Universal Mobile Telecommunications System). It can reach transfer rates up to 2 Mbps.

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GSM stands for Global System for Mobile Communications and CDMA stands for Code Division Multiple Access. They represent different systems of sharing of the radio spectrum for communication. Normally the radio spectrum can be shared by different users accessing the same frequency band without causing interference. The techniques used for this are TDMA (Time division multiple access), FDMA (Frequency division multiple access) and CDMA (Code division multiple access). GSM (Global System for Mobile Communications) is a form of multiplexing, which divides the available bandwidth among the different channels. GSM is a combination of Time and Frequency-Division Multiple Access (TDMA/FDMA). The FDMA part involves the division by frequency of the

(maximum) 25 MHz bandwidth into 124 carrier frequencies spaced 200 kHz apart. Each of these carrier frequencies is then divided in time, using a TDMA scheme. The fundamental unit of time in this TDMA scheme is called a burst period and it lasts 15/26 ms (or approx. 0.577 ms). Eight burst periods are grouped into a TDMA frame (120/26 ms, or approx. 4.615 ms), which forms the basic unit for the definition of logical channels. One physical channel is one burst period per TDMA frame. Thus GSM allows eight simultaneous calls on the same radio frequency. CDMA (Code Division Multiple Access) is a form of multiplexing (access to the same resource will be given to more than one user),which allows the use of a particular frequency for a number of signals, optimizing the use of available bandwidth. It is a cellular technology that uses spread-spectrum techniques. In CDMA technology every channel uses the full available spectrum. Individual conversations are encoded with a pseudo-random digital sequence. CDMA employs analog-to-digital conversion (ADC) in combination with spread spectrum technology. Audio input is first digitized (ADC) into binary elements. The frequency of the transmitted signal is then made to vary according to a defined pattern (code), so it can be intercepted only by a receiver whose frequency response is programmed with the same code, so it follows exactly along with the transmitter frequency. There are trillions of possible frequency-sequencing codes; this enhances privacy and makes cloning difficult. The technology is used in ultra-high-frequency (UHF) cellular telephone systems in the 800-MHz and 1.9-GHz bands. GSM was first introduced in 1991 and until recently before the establishment of CDMA networks, GSM was the only mobile communication system present in the market. CDMA was first used during World War II by the English allies to foil German attempts at jamming transmissions. The allies decided to transmit over several frequencies, instead of one, making it difficult for the Germans to pick up the complete signal. Since bandwidth is the major problem in the modern times the CDMA has a very clear advantage over the GSM in these terms. The number of channels(users) that can be allocated in a given bandwidth is comparatively higher for CDMA than for GSM. The cost of setting up a CDMA network is also comparatively less than the GSM network. Due to these advantages there is high probability that CDMA technology will dominate the future of mobile communications.

The technologies are normally evaluated on the following three parameters namely the data transmission capacity, security and radiation levels. Following table indicates the data transmission of different technologies.:Cellular technology Generation Data transmission capacity GSM CDMA (IS-95B) CDMA 2000 2G 2.5G 3G 56 Kps 64 Kps - 140 Kps 2 MBps

The idea of technology with superior security is not a new one. In 1935, a Russian researcher Dmitrii Vasilevich AGEEV, published his book "The basics of linery selection theory", where he explained the concept of coding the signals. After the WWII, Soviet and American military communication systems started to use the concept very widely because of many valuable advantages of the system. The origin concept of CDMA scheme was recommended by QUALCOMM (the famous communication provider in the US and worldwide), however Korean research institute, ETRI and companies like Hyundai, LG, and Samsung performed its realization for the first time in the world in 1995. As of today many countries have accepted it as a national standard of mobile communication and worldwide number of CDMA subscribers has climbed to over 100 million. As already explained, CDMA uses a radically different approach to what GSM does. It assigns a unique "code" to put multiple users on the same wideband channel at the same time. The codes so-called "pseudo-random code sequence" is used by both the mobile station (handset) and the base station to distinguish between conversations. This gives a greater level of privacy and security to the communication. As far as radiation level concerned, CDMA is the most harmless one among all existing technologies. Of course, it transmits microwaves while on standby mode, like other technologies do. However, CDMA technology checks 800 times per second its transmission level. Therefore, radiation level is 10 times less than GSM. Another important thing to point out is that CDMA system transmits signals only when the user starts conversation. Simply saying, when you're listening the other ends conversation, you are not affected by microwave as the speaking person does.

It appears that CDMA would be the dominating technology in future and Mobile Forensics has to gear itself to the requirements of the CDMA technology.

CDMA uses a spread-spectrum technique whereby electromagnetic energy is spread to allow for a signal with a wider bandwidth. This allows multiple people on multiple cell phones to be multiplexed over the same channel to share a bandwidth of frequencies. With CDMA technology, data and voice packets are separated using codes and then transmitted using a wide frequency range. Since more space is often allocated for data with CDMA, this standard became attractive for 3G high-speed mobile Internet use. The CDMA standard was originally designed by Qualcomm in the U.S. and is primarily used in the U.S. and portions of Asia by other carriers. Sprint,Virgin Mobile and Verizon Wireless use CDMA while T-Mobile and AT&T use GSM. While CDMA and GSM compete head on in terms of higher bandwidth speed (i.e. for surfing the mobile Web), GSM has more complete global coverage due to roaming and international roaming contracts. GSM technology tends to cover rural areas in the U.S. more completely than CDMA. Over time, CDMA won out over less advanced TDMA technology, which was incorporated into more advanced GSM. 1-G~~In the world of cell phones, 1G signifies first-generation wireless analog technology standards that originated in the 1980s. 1G was replaced by 2G wireless digital standards. 2-G~~In the world of cell phones, 2G signifies second-generation wireless digital technology. Fully digital 2G networks replaced analog 1G, which originated in the 1980s. 2G networks saw their first commercial light of day on the GSM standard. GSM stands forglobal system for mobile communications. 2G on GSM standards were first used in commercial practice in 1991 by Radiolinja, which was a Finnish GSM operator founded on Sept. 19, 1988. Radiolinja is now part of Elisa, which was known in the 1990s as the Helsinki Telephone Company. 3-G~~In addition to the GSM protocol, 2G also utilizes various other digital protocols including CDMA, TDMA, iDEN and PDC. GSM is based on TDMA. 2.5Gbridged 2G to 3G. 3G is the third generation of mobile phone standards and technology. 3G supersedes 2G technology and precedes 4G technology. 2.5G was a temporary bridge between 2G and 3G. 3G technologies enabled faster data-transmission speeds, greater network capacity and more advanced network services. The first pre-commercial 3G network launched in May 2001 by NTT DoCoMo in Japan. The network was branded as FOMA. Following the first pre-commercial launch, NTT DoCoMo again made history with the first commercial launch of 3G in Japan on Oct. 1, 2001. 4-G~~ Following the evolutionary line of cell phone technology standards that has spanned from 1G, 2G, 2.5G to 3G, 4G describes the entirely brave new world beyond

advanced 3G networks. 4G, which is also known as beyond 3G or fourth-generation cell phone technology, refers to the entirely new evolution and a complete 3G replacement in wireless communications. Just as data-transmission speeds increased from 2G to 3G, the leap from 3G to 4G again promises even higher data rates than existed in previous generations. 4G promises voice, data and high-quality multimedia in real-time (streamed) form all the time and anywhere. Various standardization and regulatory bodies estimate the launch of 4G networks commercially between 2012 and 2015.

{{http://mobiletechtime.com/?p=28Wikipedia

Cdma Chipsets CDMA Chipsets is a popular Chipsets used in 3G and 2G mobile phonesmanufactured by Qualcomm Inc.} }

CDMA Technology.ppt (Size: 302 KB / Downloads: 79) An Introduction To CDMA Technology

Introduction Short for Code Division Multiple Access Developed by US company -QUALACOMM Digital technology for delivering mobile telephone services uses spread-spectrum techniques IS-95 CDMA is based on IS-95 Technology Supports 95 million subscribers worldwide Network operate in 800 & 1900 freq. band Provides voice & data services having speed upto 64 kbits/sec SMS services also Benefits of CDMA Increased Capacity Improved Quality Simplified System Planning Enhanced Privacy Improved Coverage Increased Portable Talk Time Bandwidth on Demand

CDMA-Applications CDMA for Cellular CDMA-Short Message Service Over-the-Air Activation CDMA Data and Fax Subscriber Access Control CDMA for Personal Communications Services Conclusion

Technology of choice for 3G generation because of its Greater total capacity Outstanding voice quality Fewer dropped calls RF planning and implementation isReference: http://www.seminarprojects.com/Thread-cdma-technology-full-downloadseminar-report-and-paper-presentation#ixzz0uVbGro00

CDMA Technology Abstract : CDMA was developed by QUALCOMM Incorporated, a company in San Diego, California. QUALCOMM engineers decided to do something different and applied spread spectrum techniques to a multiple access system, which ultimately became CDMA. In spread spectrum, instead of giving each person a channel, or each group of 3 or 8 people a time slot, CDMA puts everyone in the same channel at the same time. At first thought, it would seem to be an impossible task to make work, but it does work. The reason it works is explained in the first two words of CDMA, Code Division. Each user in the system is separated from every other user by a unique digital code. And, to make sure everyone could have one of these codes of their own, engineers designed 4.4 trillion of them into the system specification. The fact is, each user is provided their own code for the reverse link. On the forward link, a group of codes is available for users of the system. There is a little more digital processing going on here that will be explained in more detail later. For now, once CDMA processing is complete, the information is converted to an RF signal and sent out over the air link. Reference: http://www.seminarprojects.com/Thread-cdma-technology-full-downloadseminar-report-and-paper-presentation#ixzz0uVbRrFM8

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http://sciencestage.com/v/22445/lecture-39-gsm-and-cdma-(contd.).html http://www.authorstream.com/Presentation/medoia-86139-cdma-education-pptpowerpoint/

ACCESS SCHEMES For radio systems there are two resources, frequency and time. Division by frequency, so that each pair of communicators is allocated part of the spectrum for all of the time, results in Frequency Division Multiple Access (FDMA). Division by time, so that each pair of communicators is allocated all (or at least a large part) of the spectrum for part of the time results in Time Division Multiple Access (TDMA). In Code Division Multiple Access (CDMA), every communicator will be allocated the entire spectrum all of the time. CDMA uses codes to identify connections.

Multiple Access Schemes CODING CDMA uses unique spreading codes to spread the baseband data before transmission. The signal is transmitted in a channel, which is below noise level. The receiver then uses a correlator to despread the wanted signal, which is passed through a narrow bandpass filter. Unwanted signals will not be despread and will not pass through the filter. Codes take the form of a carefully designed one/zero sequence produced at a much higher rate than that of the baseband data. The rate of a spreading code is referred to as chip rate rather than bit rate. See coding process page for more details.

CDMA spreading CODES CDMA codes are not required to provide call security, but create a uniqueness to enable call identification. Codes should not correlate to other codes or time shifted version of itself. Spreading codes are noise like pseudo-random codes, channel codes are designed for maximum separation from each other and cell identification codes are balanced not to correlate to other codes of itself. See codes page for more details.

Example OVSF codes, used in channel coding THE SPREADING PROCESS WCDMA uses Direct Sequence spreading, where spreading process is done by directly combining the baseband information to high chip rate binary code. The Spreading Factor is the ratio of the chips (UMTS = 3.84Mchips/s) to baseband information rate. Spreading factors vary from 4 to 512 in FDD UMTS. Spreading process gain can in expressed in dBs (Spreading factor 128 = 21dB gain). See spreading page for more details.

CDMA spreading

POWER CONTROL CDMA is interference limited multiple access system. Because all users

transmit on the same frequency, internal interference generated by the system is the most significant factor in determining system capacity and call quality. The transmit power for each user must be reduced to limit interference, however, the power should be enough to maintain the required Eb/No (signal to noise ratio) for a satisfactory call quality. Maximum capacity is achieved when Eb/No of every user is at the minimum level needed for the acceptable channel performance. As the MS moves around, the RF environment continuously changes due to fast and slow fading, external interference, shadowing , and other factors. The aim of the dynamic power control is to limit transmitted power on both the links while maintaining link quality under all conditions. Additional advantages are longer mobile battery life and longer life span of BTS power amplifiers See UMTS power control page for more details. HANDOVER Handover occurs when a call has to be passed from one cell to another as the user moves between cells. In a traditional "hard" handover, the connection to the current cell is broken, and then the connection to the new cell is made. This is known as a "break-before-make" handover. Since all cells in CDMA use the same frequency, it is possible to make the connection to the new cell before leaving the current cell. This is known as a "make-before-break" or "soft" handover. Soft handovers require less power, which reduces interference and increases capacity. Mobile can be connected to more that two BTS the handover. "Softer" handover is a special case of soft handover where the radio links that are added and removed belong to the same Node B. See Handover page for more details.

CDMA soft handover

MULTIPATH AND RAKE RECEIVERS One of the main advantages of CDMA systems is the capability of using signals that arrive in the receivers with different time delays. This phenomenon is called multipath. FDMA and TDMA, which are narrow band systems, cannot discriminate between the multipath arrivals, and resort to equalization to mitigate the negative effects of multipath. Due to its wide bandwidth and rake receivers, CDMA uses the multipath signals and combines them to make an even stronger signal at the receivers. CDMA subscriber units use rake receivers. This is essentially a set of several receivers. One of the receivers (fingers) constantly searches for different multipaths and feeds the information to the other three fingers. Each finger then demodulates the signal corresponding to a strong multipath. The results are then combined together to make the signal stronger. ---------------------------------------------WCDMA WCDMA Spreading TDD WCDMA uses spreading factors 4 - 512 to spread the base band data over ~5MHz band. Spreading factor in dBs indicates the process gain. Spreading

factor 128 = 21 dB process gain). Interference margin is calculated from that: Interference Margin = Process Gain - (Required SNR + System Losses) Required Signal to Noise Ration is typically about 5 dB System losses are defined as losses in receiver path. System losses are typically 4 - 6 dBs

Overview of Spreading Process 3G and LAN Date Speeds Here are the theoretical maximum data speeds of 2G, 2.5G, 3G and beyond, and compared to LAN data speeds.

Data Speed of Mobile Systems (top) and LANs (bottom) 3G and UMTS Technology Mobile data communications is evolving quickly because of Internet, Intranet, Laptops, PDAs and increased requirements of workforce mobility. 3G UMTS will be the commercial convergence of fixed line telephony,

mobile, Internet and computer technology. New technologies are required to deliver high speed location and mobile terminal specific content to users. The emergence of new technologies thus provides an opportunity for a similar boom what the computer industry had in 1980s, and Internet and wireless voice had in 1990s. The main IMT-2000 standardisation effort was to create a new air interface that would increase frequency usage efficiency. The WCDMA air interface was selected for paired frequency bands (FDD operation) and TDCDMA (TDD operation) for unpaired spectrum. 3G CDMA2000 standard was created to support IS-95 evolution. The UMTS transport network is required to handle high data traffic. A number of factors were considered when selecting a transport protocol: bandwidth efficiency, quality of service, standardisation stability, speech delay sensitivity and the permitted maximum number of concurrent users. In the UMTS network, ATM (Asynchronous Transfer Mode) is defined for the connection between UTRAN and the core network and may also be used within the core network. In addition to the IMT-2000 frame many new standards will be integrated as part of the next generation mobile systems. Bluetooth and other close range communication protocols and several different operating systems will be used in mobiles. Internet will come to mobiles with WAP, i-mode and XML protocols. 3G development has helped to start the standardisation and development of large family of technologies. This section covers some of the core UMTS technologies and it will be updated regularly. 3G Network Planning Basics1. Planning 2. Coverage Planning 3. Capacity Planning 4. General Guidelines 5. Radio Access Network Design 6. Core Network Design 7. Transmission Design 8. The Summary

Cdma2000 Cdma2000 specification was developed by the Third Generation Partnership Project 2 (3GPP2), a partnership consisting of five telecommunications standards bodies: ARIB and TTC in Japan, CWTS in China, TTA in Korea and TIA in North America. Cdma2000 has already been implemented to several networks as an evolutionary step from cdmaOne as cdma2000 provides full backward compatibility with IS-95B. Cdma2000 is not constrained to only the IMT-2000 band, but operators can also overlay acdma2000 1x system, which supports 144 kbps now and data rates up to 307 kbps in the future, on top of their existing cdmaOne network. The evolution of cdma2000 1x is labeled cdma2000 1xEV. 1xEV will be implemented in steps: 1xEV-DO and 1xEV-DV. 1xEV-DO stands for "1x Evolution Data Only". 1xEV-DV stands for "1x Evolution Data and Voice". Both 1xEV cdma2000 evolution steps will use a standard 1.25 MHz carrier. 1xEV-DO probably will be available for cdma2000 operators during 2002 and 1xEV-DV solutions will be available approximately late 2003 or early 2004. Cdma2000 1x EV-DO and cdma2000 3x are an ITU-approved, IMT-2000 (3G) standards. Cdma2000 3x is part of what the ITU has termed IMT-2000 CDMA MC (Multi Carrier). It uses less that 5 MHz spectrum (3x 1.25 MHz channels) to give speeds of over 2 Mbps. Cdma2000 1x with lower data speed is considered to be a 2.5G technology.

Cdma2000 Technical summary Frequency band: Any existing band. Minimum frequency band required: 1x: 2x1.25MHz, 3x: 2x3.75 Chip rate: 1x: 1.2288, 3x: 3.6864 Mcps Maximum user data rate: 1x: 144 kbps now, 307 kbps in the future 1xEVDO: max 384 kbps - 2.4 Mbps, 1xEV-DV: 4.8 Mbps. Frame length: 5ms, 10ms or 20ms Power control rate: 800 Hz Spreading factors: 4 ... 256 UL

TDCDMA UTRA TDD is planned to operate in the unpaired spectrum. TDD uses a combined time division and code division multiple access scheme. It is base on radio access technique proposed by ETSI Delta group and the specifications was finalised 1999.

TDD Technical Summary Frequency band:1900 MHz -1920 MHz and 2010 MHz - 2025 MHz (Time Division Duplex) Unpaired, channel spacing is 5 MHz and raster is 200 kHz. Tx and Rx are not separated in frequency, but by guard period. Minimum frequency band required: ~ 5MHz, ~ 1.6MHz with 1.28 Mcps Frequency re-use: 1 Voice coding: AMR (and GSM EFR) codec Channel coding: Convolutional coding, Turbo code for high rate data TDMA frame consist of 15 timeslots Each time slot can be transmit of receive Duplexer not needed Asymmetric connection supported Data by packet and circuit switch QPSK modulation Receiver: Joint Detection, (mobile: Rake) Chip rate: 3.84 Mcps or 1.28 Mcps Channel raster: 200 kHz Maximum RF ch bit rate (kbps): ~ 3.3Mbps (1/2 rate coding, spreading factor 1, 15 timeslots, ex overheads), but interference limited Frame length: 10ms Number of slots / frame: 15 Handovers: Hard Power control period: 100 Hz or 200 Hz UL, ~ 800 Hz DL Power control step size: 1, 2, 3 dB (Variable) Power control range: UL 65dB, DL 30dB Mobile peak power: Power class 1: +33 dBm (+1dB/-3dB) = 2W; class 2 +27 dBm, class 3 +24 dBm, class 4 +21 dBm

Number of unique base station identification codes: 512/frequency Physical layer spreading factors: 1, 2, 4, 8, 16 WCDMA (UMTS) Wideband Code-Division Multiple-Access (W-CDMA) is one of the main technologies for the implementation of third-generation (3G) cellular systems. It is base on radio access technique proposed by ETSI Alpha group and the specifications was finalised 1999. The implementation of W-CDMA will be a technical challenge because of it's complexity and versatility. The complexity of W-CDMA systems can be viewed from different angles: the complexity of each single algorithm, the complexity of the overall system and the computational complexity of a receiver. W-CDMA link-level simulations are over 10 times more computeintensive than current second-generation simulations. In W-CDMA interface different users can simultaneously transmit at different data rates and data rates can even vary in time. UMTS networks need to support all current second generation services and numerous new applications and services. FDD Technical summary Frequency band:1920 MHz -1980 MHz and 2110 MHz - 2170 MHz (Frequency Division Duplex) UL and DL [more] Minimum frequency band required: ~ 2x5MHz Frequency re-use: 1 Carrier Spacing: 4.4MHz - 5.2 MHz Maximum number of (voice) channels on 2x5MHz: ~196 (spreading factor 256 UL, AMR 7.95kbps) / ~98 (spreading factor 128 UL, AMR 12.2kbps) Voice coding: AMR codecs (4.75 kHz - 12.2 kHz, GSM EFR=12.2 kHz) and SID (1.8 kHz) Channel coding: Convolutional coding, Turbo code for high rate data Duplexer needed (190MHz separation), Asymmetric connection supported Tx/Rx isolation: MS: 55dB, BS: 80dB Receiver: Rake Receiver sensitivity: Node B: -121dBm, Mobile -117dBm at BER of 10-3 Data type: Packet and circuit switch Modulation: QPSK Pulse shaping: Root raised cosine, roll-off = 0.22

Chip rate: 3.84 Mcps Channel raster: 200 kHz Maximum user data rate (Physical channel): ~ 2.3Mbps (spreading factor 4, parallel codes (3 DL / 6 UL), 1/2 rate coding), but interference limited. Maximum user data rate (Offered): 384 kbps (year 2002), higher rates ( ~ 2 Mbps) in the near future. HSPDA will offer data speeds up to 8-10 Mbps (and 20 Mbps for MIMO systems) Channel bit rate: 5.76Mbps Frame length: 10ms (38400 chips) Number of slots / frame: 15 Number of chips / slot: 2560 chips Handovers: Soft, Softer, (interfrequency: Hard) Power control period: Time slot = 1500 Hz rate Power control step size: 0.5, 1, 1.5 and 2 dB (Variable) Power control range: UL 80dB, DL 30dB Mobile peak power: Power class 1: +33 dBm (+1dB/-3dB) = 2W; class 2 +27 dBm, class 3 +24 dBm, class 4 +21 dBm Number of unique base station identification codes: 512 / frequency Physical layer spreading factors: 4 ... 256 UL, 4 ... 512 DL WCDMA (DoCoMo) The International Telecommunication Union (ITU) officially selected Wideband Code Division Multiple Access (WCDMA) as one of the global telecom systems for the new IMT-2000 3G mobile communications standard. NTT DoCoMo is using an ARIB standardised WCDMA solution. NEC, Ericsson and Lucent were chosen as suppliers to the 3G network named FOMA. More: Arib IMT-2000 page and 3G frequency plan page FOMA WCDMA Technical summary Frequency band:1920-1980 and 2110-2170 MHz (Frequency Division Duplex) UL and DL Minimum frequency band required: 2x5MHz Chip rate: 4.096 Mcps Number of slots / frame: 16

TD-SCDMA Time Division Synchronous CDMA (TD-SCDMA) was proposed by China Wireless Telecommunication Standards group (CWTS) and approved by the ITU in 1999 and technology is being developed by the Chinese Academy of Telecommunications Technology and Siemens. TD-SCDMA uses the Time Division Duplex (TDD) mode, which transmits uplink traffic (traffic from the mobile terminal to the base station) and downlink traffic (traffic from the base station to the terminal) in the same frame in different time slots. That means that the uplink and downlink spectrum is assigned flexibly, dependent on the type of information being transmitted. When asymmetrical data like e-mail and internet are transmitted from the base station, more time slots are used for downlink than for uplink. A symmetrical split in the uplink and downlink takes place with symmetrical services like telephony. TD-SCDMA Technical Summary Frequency band: 2010 MHz - 2025 MHz in China (WLL 1900 MHz - 1920 MHz) Minimum frequency band required: 1.6MHz Frequency re-use: 1 (or 3) Chip rate: 1.28 Mcps Frame length: 10ms Number of slots: 7 Modulation: QPSK or 8-PSK Voice data rate: 8kbit/s Circuit switched services: 12.2 kbits/s, 64 kbits/s, 144 kbits/s, 384 kbits/s, 2048 kbits/s Packet data: 9.6kbits/s, 64kbits/s, 144kbits/s, 384kbits/s, 2048kbits/s Receiver: Joint Detection, (mobile: Rake) Power control period: 200 Hz Number of slots / frame: 7 Frame length: 5ms Multi carrier option Handovers: Hard Smart antennas Baton handover Uplink synchronisation Physical layer spreading factors: 1, 2, 4, 8, 16

Cdma2000 and UMTS were developed separately and are 2 separate ITU approved 3G standards. Cdma2000 1xRTT, cdma2000 1xEV-DO (EVolution, Data Only) and future cdma2000 3x were developed to be backward compatible with cdmaOne. Both 1x types have the same bandwidth, chip rate and it can be used in any existing cdmaOne frequency band and network. Backward compatibility was a requirement for successful deployment for USA market. It is easy to implement because operators do not need new frequencies. [more about cdma2000] UMTS was developed mainly for countries with GSM networks, because these countries have agreed to free new frequency ranges for UMTS networks. Because it is a new technology and in a new frequency band, whole new radio access network has to be build. The advantage is that new frequency range gives plenty of new capacity for operators. 3GPP is overseeing the standard development and has wisely kept the core network as close to GSM core network as possible. UMTS phones are not meant to be backward compatible with GSM systems. (but subscriptions (=SIM card) can be, and dual mode phone will solve the compatibility problems, hopefully). UMTS also has 2 flavors FDD (will be implemented first) and TDD. Some harmonisation has been done between systems (like chip rate and pilot issues) Why is WCDMA called "Wideband"? 3G WCDMA systems have 5MHz bandwidth (one direction). 5MHz is neither wide nor narrow; it is just the bandwidth. New 3G WCDMA systems have wider bandwidth than existing 2G cdma systems (cdmaOne 1.25MHz), that's why the "Wide". There are commercial cdma systems with 20MHz bandwidth. ; The fastest modems in existence today for standard phone lines (and the fastest which will everexist, because they use the full bandwidth which is available) are designed specifically for how the phone system A/D converters work. They happen to be non-linear, but the real point is that the threshold for each A/D step is published. When two of these modems establish contact with each other, they "negotiate" and test the line to see just how high an amplitude the line will permit. (They also test various steps in between to make sure they understand how the line is being amplified.) If they can get up to step 237, for instance, then thereafter they will communicate with each other in modulo 237. On each A/D digitization time (which is also published) the transmitting modem sends to the phone system a flat voltage representing one of the 237 voltages which the line permits, and thus this is what will pop out at the receiving modem. Converting binary streams into arbitrary modulus transmissions and back out again is left as an exercise to the student. So the modems are designed precisely around the exact characteristics of the land-line, in published standards. Unfortunately, CDMA cell phones work entirely differently. For one thing, while the transmissions in the land-line system are lossless (as long as you stick to the amplitude and step-function levels which the line will support) that is not the case for CDMA.

CDMA begins with a far more restricted bandwidth per phone call than a landline does. When you speak into your phone, it is digitized, but then it is passed through a lossy compression device called a codec. The codec algorithm is specifically designed to take advantage of the fact that human spoken language is enormously redundant and that the human ear can compensate for certain kinds of distortion. In fact, humans are extremely good at this, as you'll realize if you've ever had a conversation at a busy party, or next to high surf, or by a revving motorcycle. Needless to say, CDMA's codecs don't induce distortion like that. The CDMA codec deliberately discards useless detail, and by doing so is capable of achieving a tenfold reduction in the data stream -- or even more in some cases. Now the emphasis here is on the word useless. Human ears will barely notice that anything has changed, but test equipment (and modems) can pinpoint the differences very clearly. This works beautifully for a human voice, and most people find that CDMA with a 13K codec actually sounds as good as or even better than a landline does. (Landlines suffer from the fact that the voice traffic covers several miles from the last stage switch to the home, in analog, on copper wires with little shielding. Distortion and noise are inevitable.) But what the CDMA codec is doing is completely wrong for how a standard modem wants to use the link. For one thing, the traffic that a standard modem tries to feed to the phone looks nothing like a human voice, and the codec is lost at sea. If a standard modem were connected to such a phone, what would come out at the far end would bear only a passing resemblance to what went in. The negotiation between the two modems would fail completely and no connection would take place. The highest transmission rate available as this is written (May 1999) in most CDMA systems is 14.4 kilobits. There simply is no way to cram 56 kilobits through such a channel; Claude Shannon's Information Theory doesn't permit it. And even at lower rates, what the modem is feeding the phone is not what the phone is designed to carry. [Soon the cell systems will deploy a new form of data services which will support much higher data rates. SCDB 2/2000] The right solution is for digital communications through CDMA to take advantage of the characteristics of the medium, just as it does through a landline. In this case, it takes advantage of the fact that the actual link between the cell system and the phone is digital, unlike landlines. When the phone carries digital data, it bypasses the codec entirely and transmits the digital information given it by some external digital device (typically a notebook computer or PIM). At the cell system the resulting digital stream either is passed through a standard modem before interfacing into the standard landline phone system, or increasingly it will be gatewayed directly onto the Internet. By this means, the full digital bandwidth of the phone channel is made available to the user.

Is it possible to jam CDMA? Short answer: It's possible, but it's impractical. Long answer: People who ask this question tend to divide into two groups. The first group are those who are concerned about people who are stupid enough to use their cell phones in environments where the radio frequency emissions (RF) could cause problems, like near operating jets, or in hospitals where people are wired to pacemakers. The second group are those who are fed up with listening to phones ringing in theaters and restaurants. RF jamming divides into active and passive. Passive jamming means shielding; the ultimate form of this is known as a "Faraday cage" and it means you are surrounded by conductive metal or fine screen on all sides, including top and bottom. Active jamming means to broadcast meaningless RF at the frequencies in question at sufficient power level to disrupt the behavior of the device -- in this case, the CDMA cell phone. Active jamming is a lost cause. Not only would it be a violation of FCC regulations (or those of comparable authorities in other countries) but CDMA uses spread spectrum. Spread spectrum was developed during World War 2 precisely because it is exceedingly difficult to jam with active jamming. And in many cases (the hospital heart ward) the cure would be worse than the disease because the transmit power levels required would cause more harm than the phones could.

Passive jamming would require that metallic shielding be built into the walls of the structure as it was being constructed. While this might work for a theater, it's impossible for any structure which has windows unless you put grounded screens over every single one of them. (Which might actually be possible for the heart ward, but is probably impractical for a restaurant or an airport.) And it certainly wouldn't be cheap in any case. How easy is it to eavesdrop on CDMA cellular? Short answer: Harder than a landline phone. Long answer: Eavesdropping on the radio link is prohibitively difficult. Any law enforcement agency which wanted to listen to your calls wouldn't bother with that. The cellular and PCS carriers are required to cooperate with law enforcement agencies armed with proper warrants for line taps. If they wish to listen to calls, they tap in at the service provider's central office. It's approximately comparable to what they would do to tap a landline phone. It's possible to illicitly tap a landline by having someone climb a phone pole (or go down into a hole) and tap the wires near your home. The equivalent of this for AMPS was a simple FM radio scanner that cost a few hundred dollars. But whoever decided to try something like that for CDMA would be stumped. Even if he had all the information necessary (like your phone's ESN, which is required to be able to intercept the reverse link) the equipment needed would cost tens of thousands of dollars, well beyond the means of any private detective or creepy voyeur. When you speak into your CDMA phone, your voice is digitized and compressed into 50 digital packets per second. These are then spread, interleaved, passed through a Viterbi forward-errorcorrection encoder, scrambled using the Walsh code for the channel you've been assigned, scrambled again with the short code, possibly encrypted, scrambled yet again with a modified version of the long code and then transmitted in quadrature with spread spectrum. The creepy voyeur with his FM scanner can't even pick up spread spectrum, and if he had the right receiver it would just sound like a very high frequency hiss (well beyond the range of human hearing) bearing no resemblance whatever to your voice. The modification of the long code includes knowledge of the ESN (the unique serial number of your phone) which the phone keeps in its memory and the cell system knows. The ESN is not transmitted, and thus can't be intercepted. Rather, your phone sends its phone number to the cell system, which looks the ESN up in its database. (If you're roaming, it gets it from your home system.) Both your phone and the cell system know the ESN and modify the long code the same way. Without it, the resulting chip sequence is gibberish. It would not only take a lot of very expensive and customized hardware to do all this, it would also take espionage. It's been truly said that if you have someone after you who can intercept your CDMA radio link and is inclined to do so, you've got a lot worse problems than just this. Short answer: There's an ideal length for the antenna. Long answer: The ideal length of an antenna is half a wavelength of whatever the frequency is that it's designed to operate with. 800 MHz cellular has a wavelength of approximately 37 centimeters, about 15 inches. So an ideal antenna would be half that, about seven and a half inches. This refers to the dipole, the distance from the tip of the antenna to the opposite end of the antenna buried inside the phone somewhere (usually near the bottom). 1900 MHz PCS has a wavelength of approximately 16 centimeters, about six inches. So the ideal antenna dipole is about 3 inches. The ideal antenna performs best if it is exactly perpendicular to the impinging waveform. In practice the orientation of the phone is somewhat random; the antenna will be pointed approximately upward, but probably at a slant. So cell phone manufacturers generally try to make the antenna 5/8's of a waveform, because if the antenna is at a slant, its cross-section relative to the impinging waveform will be near to the ideal half a wavelength. For a dual-band phone, one which operates at both 1900 and at 800 MHz, it's obvious that determining the antenna length is a bit of a problem.

(But not insoluble; it's just a compromise. Since digital is usually more resilient than AMPS, usually the length is optimized for 800 MHz.) Making the antenna shorter will both decrease the amount of incoming signal the phone receives, and will make the phone's transmitter less efficient. But CDMA operates over a very wide range of effective powers, and it can usually compensate. That's why the phone will usually work with the antenna down. And because it's digital, if it is working it will sound exactly the same. This has lead some people to conclude that the antenna is not actually doing anything for them, which is not quite correct. While the phone can operate with the antenna down, it's easier on the phone if you raise the antenna; it has more signal ceiling to work with and will be less likely to drop the call. Also, it will use somewhat less transmit power, and your battery will last somewhat longer. Making it longer with some sort of extension is worse than useless; it actually degrades the signal. If the antenna is exactly one wavelength long and is exactly perpendicular to the impinging waveform, it will pick up essentially no signal at all. When it reaches one and a half wavelengths, signal strength is again maximized, but for physical reasons it's a bit lower than the strength with a half-wavelength antenna. (The physical reason is that the antenna is not an ideal conductor.) Short answer: The network tells it. Long answer: CDMA requires that every component of the system, including all the handsets, have a very precise knowledge of exactly what absolute time it is. This is necessary in order to synchronize the long code, one of the modulating chip-patterns used to make spread spectrum work. The long code cycles only once every six weeks (41.4 days) and if the phone's long code is out of sync, it won't work with the network. What follows is a bit esoteric, since it gets into the guts of how CDMA works. The system acquisition process involves three steps. In the first step it has to find the pilot. The pilot is channel 0 (whose Walsh Code is all zeros) and it broadcasts a signal of constant zeros, which is not modulated with the long code. In essence, that means that what it is transmitting is the cell's short-code at whatever phase offset the cell is using. (Phase offset of the short code is how cells are differentiated from each other, since they all use the same frequencies.) Once the phone has found that, it can synchronize its short code. Step 2 is to find the sync channel and to process a sync channel message. The sync channel message contains many interesting things, but one of the things it contains is "At the tone, the time will be...". Actually, the "tone" is the next PNROLL(0), which is known to cognoscenti as an "80" because they happen every 80 milliseconds. (It's the next time that the PNROLL, which happens every 26.666 milliseconds, coincides with a frame, which happens ever 20 milliseconds. There are three PNROLLs for every four frames.) The sync channel message also tells the phone what timezone the cell is in (in increments of plus or minus half hour relative to Universal Time) and the number of leap seconds there have been since "the beginning of time" (which happens to be time 0 for GPS, sometimes called the epoch. It happens to have been midnight on January 6, 1980.) Note that the cell and phone won't necessarily be in the same time zone, which is why your phone may seem to be an hour off if you're right next to a time-zone line. That happens if it synchronized with a cell on the opposite side of the line. This idea of the time is accurate to a few microseconds. The inaccuracy comes from the speed of light delay between the cell and the phone, and the fact that the phone doesn't know how far away the cell is. (The speed of light is about 980 feet per microsecond, almost exactly 300 meters. If you're a mile from a cell, then it takes about five microseconds for the signal to reach you.) It would actually be useless to know that delay. The purpose of knowing the time is to permit initialization of the long code generator, and the long code being received from the cell is being delayed by the same amount of time as the sync channel message was. Therefore, it's good that the sync channel message is delayed by the transmission path length. Once the phone initializes its long code generator, it moves to step 3, which is to listen to the

paging channel. After that, if it doesn't decide that it can't use that cell, it will register, and then your phone is online. This always happens when you first power up your phone. It always happens just after you finish a call. It happens at other times, too. Whenever the phone processes a sync-channel message, it sets its internal representation of the time of day. On most phones, that's what's being displayed on the screen. The IS-95 specification requires that all the cells be synchronized to within a few microseconds of each other. In actuality, they do it by having a fixed GPS receiver at each cell, from which the equipment gets the time very precisely. Most CDMA phones don't let you manually set the time of day, mostly because doing so would be pretty useless. The phone would override your time each and every time it acquired a cell, anyway. So why does the minute display on my phone click over several seconds late compared to WWV? The phone is usually in a mode called slotted sleep during which as much of the phone as is possible is shut down to save power, including the CPU. There would be a significant power cost (manifesting as a significant hit on standby time) in order for the phone to update its display more often during slotted sleep. You might note that the "elapsed time" display during a call ticks seconds very accurately. That's because the CPU is on anyway to handle the call, so there's no additional cost to speak of in maintaining the display accurately. reemusk ow is CDMA superior to TDMA? Short answer: It supports more calls in the same spectrum, and it dynamically allocates bandwidth more easily. Long answer: Spectrum is extremely expensive; it has to be purchased from various governmental licensing authorities at auction, and sometimes these auctions have involved billions of dollars (or equivalent monetary value in other currencies). It represents a considerable investment by a carrier. Generally speaking, CDMA will carry between two and three times as many calls simultaneously as TDMA in the same amount of bandwidth. This is due to something known as "frequency reuse" and is very well explained on this page. The other major advantage of CDMA is dynamic allocation of bandwidth. To understand this, it's important to realize that in this context in CDMA, "bandwidth" refers to the ability of any phone to get data from one end to the other. It doesn't refer to the amount of spectrum used by the phone, because in CDMA every phone uses the entire spectrum of its carrier whenever it is transmitting or receiving. TDMA works by taking a channel with a fixed bandwidth and dividing it into time slots. Any given phone is then given the ability to use one or more of the slots on an ongoing basis, if it is in a call. For instance, if the channel is 200 kHz wide with 8 slots, and the phone is allocated one of them, then the phone has effective bandwitdth of 200/8 = 25 kHz. This bandwidth is allocated to that phone while the call proceeds, whether the phone actually uses it or not. In other words, when you're in a call with TDMA and being silent because you're listening to the other person speak, your phone still uses that full bandwidth to transmit silence. CDMA is more efficient about that kind of thing. In both TDMA and CDMA, the outgoing voice traffic is digitized and compressed. But the CDMA codec can realize when the particular packet is noticeably simpler (e.g. silence, or a sustained tone with little change in modulation) and will compress the packet far more. Thus the packet may involve fewer bits, and the phone will take less time to transmit it. And that's where this odd idea of what "bandwidth" means in CDMA comes in. For in a very real sense, bandwidth in CDMA equates to received power at the cell. CDMA systems constantly adjust

power to make sure as little is used as necessary, and compensate for this by using coding gain through the use of forward error correction and other approaches which are much too complicated to go into here. The chip rate is constant, and if more actual data is carried by the constant chip rate, then there will be less coding gain. Therefore, it's necessary to use more power instead. Conceptually, a given cell sector can tolerate a certain amount of total received power before it becomes difficult to decipher all the channels being received. If one phone uses more of that power allocation, there is less available for the others. But this is an advantage, not a disadvantage, for it can be stated a different way: if one phone uses less of that power allocation, there is more available for the others. This is the right way to look at it, because this is going on constantly. In a TDMA system, suppose that the phone needed more or less than the 25 kHz slot. "Less" is a non-issue because there's no way to get smaller. "More" would require that an additional slot be allocated to the phone, which would require a protocol-level exchange: the phone says to the cell "I need more bandwidth", the cell finds some other phone on that same channel and tells it to move, clearing an additional slot, then sends a message back to the phone telling it "OK, you can use this slot in addition". This might take quite a while, and by the time it's complete the need may have passed. But CDMA actually does this dynamically and on the fly. When the CDMA phone realizes that it doesn't need to transmit a full digital packet, it will use a "half rate" packet, or "quarter rate" or "eighth rate", and will transmit for less time. Packet transmissions happen fifty times per second in current CDMA systems, but a phone with a half-rate packet to send will pseudo-randomly send half the symbols during the 20 millisecond packet. Received power at the cell is an instantaneously measured quantity. If two phones are transmitting at half rate but at different times, the cell is actually only receiving power from one phone at a time. Effective bandwidth in CDMA is thus actually being dynamically allocated at all times. And when you are listening and silent, the phone drops to eighth rate and uses virtually no bandwidth at all. This is very nice for voice traffic and is an additional reason why CDMA is more efficient in use of spectrum, but where it will become particularly valuable is when data transmission becomes a significant use. That's because common data use is very bursty, even more than is voice traffic. Consider how you use a browser, for instance: you click a link and in a short interval your computer downloads many kilobytes of data. You then sit and read what was downloaded, and there's virtually no data traffic going on. In a CDMA system, it would be very easy to allocate a considerable proportion of the bandwidth of a sector to a single phone for that interval. Nothing special needs to be done except to allocate that phone a considerable proportion of the power, which it could do without requesting permission from the cell. High spectrum efficiency and dynamic allocation of bandwidth are the principle reasons why the entire wireless telecommunications industry is moving to CDMA. The current generation of GSM is based on TDMA, but the next generation will use a CDMA air interface. What is "Soft Handoff"? Short answer: One of the advantages of CDMA over TDMA. Long answer: In TDMA or AMPS, due to spectrum reuse, a given slot on a given frequency channel can't be used by neighboring cells. So when a phone which is in a call moves from one cell to another, at a certain point it has to switch between cells. In AMPS and TDMA it will be commanded by the system to change frequencies, all at once. This is called a hard handoff, so called because it's all or nothing: the transition is a hard one. In CDMA, on the other hand, all the cells operate on the same frequency. The phone still has a single RF receiver which converts radio frequency down to baseband, but behind that it has a rake receiver with multiple fingers. Since all the cells operate on the same frequency, the single RF

receiver picks up all of those which are within range. The phone then assigns fingers from the rake receiver to various signals, and these are added together to create the full signal the phone utilizes. Sometimes these are multiple paths from the same cell. For instance, if there's a direct route from the cell to the phone, and in addition the signal travels to a large building and reflects off it before reaching the phone, then the CDMA phone can utilize both of these signals for additional clarity. This is called multipath. (Similar conditions degrade TDMA and AMPS performance.) But even more useful is when the phone is about halfway between two cells. While in a call, the phone is not only handling its transport of data back and forth to the cell, but it's also actively looking for other cells. When it finds one whose signal strength is good (on the same frequency, remember) it will inform the cell system of this. The cell system might decide at that point to route the call through both cells simultaneously. The specification actually permits a phone to talk to six cells at once, though no phone currently in existence has this capability. So when a CDMA phone in a call moves from one cell to another, the handoff process happens in multiple steps. First the phone notices the second cell, and the cell begins to carry the call on both cells. As the phone continues to move, eventually the signal strength from the one the phone is moving away from will drop to the point where it isn't useful any longer. Again, the phone will inform the cell system of this fact, and the system will drop the original cell. Thus it isn't an all-ornothing transition, which is why it is called soft. ,,,,is

it possible to jam CDMA?

Short answer: It's possible, but it's impractical. Long answer: People who ask this question tend to divide into two groups. The first group are those who are concerned about people who are stupid enough to use their cell phones in environments where the radio frequency emissions (RF) could cause problems, like near operating jets, or in hospitals where people are wired to pacemakers. The second group are those who are fed up with listening to phones ringing in theaters and restaurants. RF jamming divides into active and passive. Passive jamming means shielding; the ultimate form of this is known as a "Faraday cage" and it means you are surrounded by conductive metal or fine screen on all sides, including top and bottom. Active jamming means to broadcast meaningless RF at the frequencies in question at sufficient power level to disrupt the behavior of the device -- in this case, the CDMA cell phone. Active jamming is a lost cause. Not only would it be a violation of FCC regulations (or those of comparable authorities in other countries) but CDMA uses spread spectrum. Spread spectrum was developed during World War 2 precisely because it is exceedingly difficult to jam with active jamming. And in many cases (the hospital heart ward) the cure would be worse than the disease because the transmit power levels required would cause more harm than the phones could. Passive jamming would require that metallic shielding be built into the walls of the structure as it was being constructed. While this might work for a theater,

it's impossible for any structure which has windows unless you put grounded screens over every single one of them. (Which might actually be possible for the heart ward, but is probably impractical for a restaurant or an airport.) And it certainly wouldn't be cheap in any case. Can I use a normal modem with my CDMA cell phone? Short answer: No. Long answer: Sorry, but the long answer is really long. This isn't a plot by the cell phone manufacturers to force you to discard your perfectly good modem. To understand why, you have to understand how normal modems work and how they relate to the regular land-line phone system. Originally the phone system was a circuit switch, and modems were analog. This is in the days of the cross-bar switch, and after a circuit had been established a single wire carried traffic both ways (possibly with an analog amplifier in between). Modems were devices which moved digital information from one place to another using what was known as "frequency shift keying". That meant that the modem alternated between two frequencies when it transmitted, with one frequency meaning "1" and the other "0". Time marches on, and the modems got faster. The new approach was called "phase shift keying", and it worked by encoding four bits into a single wave. There things stalled. Meanwhile, the phone companies had been switching to digital systems which were not cross-bars. Instead, they worked by digitizing the analog waveform being fed to them, packetizing the results, and interleaving it at very high speed into a TDMA bit stream inside the switch. So to connect two lines to each other, instead of a physical switch making an electrical connection between them, the switch tells each which TDMA time slot to use. This massively simplifies the switch and improves reliability by removing all the mechanical moving parts which were associated with the older cross-bar approach. But it also meant that the connection from one end of the phone line to the other was no longer electrically isolated. Rather, it was being digitized and thus converted to a step function. Any approach which depended on pure analog

waveforms was doomed to fail. But it opened the way for a crafty approach to modem design. The fastest modems in existence today for standard phone lines (and the fastest which will ever exist, because they use the full bandwidth which is available) are designed specifically for how the phone system A/D converters work. They happen to be non-linear, but the real point is that the threshold for each A/D step is published. When two of these modems establish contact with each other, they "negotiate" and test the line to see just how high an amplitude the line will permit. (They also test various steps in between to make sure they understand how the line is being amplified.) If they can get up to step 237, for instance, then thereafter they will communicate with each other in modulo 237. On each A/D digitization time (which is also published) the transmitting modem sends to the phone system a flat voltage representing one of the 237 voltages which the line permits, and thus this is what will pop out at the receiving modem. Converting binary streams into arbitrary modulus transmissions and back out again is left as an exercise to the student. So the modems are designed precisely around the exact characteristics of the land-line, in published standards. Unfortunately, CDMA cell phones work entirely differently. For one thing, while the transmissions in the land-line system are lossless (as long as you stick to the amplitude and step-function levels which the line will support) that is not the case for CDMA. CDMA begins with a far more restricted bandwidth per phone call than a landline does. When you speak into your phone, it is digitized, but then it is passed through a lossy compression device called acodec. The codec algorithm is specifically designed to take advantage of the fact that human spoken language is enormously redundant and that the human ear can compensate for certain kinds of distortion. In fact, humans are extremely good at this, as you'll realize if you've ever had a conversation at a busy party, or next to high surf, or by a revving motorcycle. Needless to say, CDMA's codecs don't induce distortion like that. The CDMA codec deliberately discards useless detail, and by doing so is capable of achieving a tenfold reduction in the data stream -- or even more in some cases. Now the emphasis here is on the worduseless. Human ears will barely notice that anything has changed, but test equipment (and modems) can pinpoint the differences very clearly.

This works beautifully for a human voice, and most people find that CDMA with a 13K codec actually sounds as good as or even better than a landline does. (Landlines suffer from the fact that the voice traffic covers several miles from the last stage switch to the home, in analog, on copper wires with little shielding. Distortion and noise are inevitable.) But what the CDMA codec is doing is completely wrong for how a standard modem wants to use the link. For one thing, the traffic that a standard modem tries to feed to the phone looks nothing like a human voice, and the codec is lost at sea. If a standard modem were connected to such a phone, what would come out at the far end would bear only a passing resemblance to what went in. The negotiation between the two modems would fail completely and no connection would take place. The highest transmission rate available as this is written (May 1999) in most CDMA systems is 14.4 kilobits. There simply is no way to cram 56 kilobits through such a channel; Claude Shannon's InformationTheory doesn't permit it. And even at lower rates, what the modem is feeding the phone is not what the phone is designed to carry. [Soon the cell systems will deploy a new form of data services which will support much higher data rates. SCDB 2/2000] The right solution is for digital communications through CDMA to take advantage of the characteristics of the medium, just as it does through a landline. In this case, it takes advantage of the fact that the actual link between the cell system and the phone is digital, unlike landlines. When the phone carries digital data, it bypasses the codec entirely and transmits the digital information given it by some external digital device (typically a notebook computer or PIM). At the cell system the resulting digital stream either is passed through a standard modem before interfacing into the standard landline phone system, or increasingly it will be gatewayed directly onto the Internet. By this means, the full digital bandwidth of the phone channel is made available to the user.

IS-95 is a standard for

CDMA (Code Division Multiple Access) Digital Cellular .

Mobile Frequency Range Multiple Access Method Duplex Method Number of Channels Channel Spacing Modulation

Rx: 869-894; Tx: 824-849 CDMA/FDM FDD 20 (798 users per channel) 1250kHz QPSK/OQPSK

Channel Bit Rate How CDMA Works

1.2288Mb

In a CDMA system, your encoded voice is digitized and divided into packets. These packets are tagged with "codes." The packets then mix with all of the other packets of traffic in the local CDMA network as they are routed towards their destination. The receiving system only accepts the packets with the codes destined for it.

CDMA vs. TDMAThe CDMA technology used in IS-95 is in technical competition with the TDMA (Time Division Multiple Access) technology used in GSM.

IS-95 by Any Other NameIS-95 is also known as TIA-EIA-95. The original IS-95 CDMA specification is now referred to ascdmaOne.

Newer CDMA StandardsNewer CDMA standards include cdma2000, CDMA 1X EV, CDMA 1XEV-DO, CDMA MC 3X, WCDMA and TD-SCDMA. CDMA-2000 1xRTT is a recent standard for data networking over CDMA-2000 networks.

CDMA Network OperatorsALLTEL, Verizon Wireless , US Cellular, and Qwest communications operate CDMA networks within the United States. Worldwide, there are over 60 million users of IS-95 and other CDMA networks.

Additional Reading on CDMAFor more information on CDMA, visit the CDMA Development Group.

What is CDMA?

What is 1x?

What is CDMA? (#7400)Code Division Multiple Access (CDMA) is a digital wireless technology that was pioneered and commercially developed by Qualcomm. CDMA works by converting speech into digital information, which is then transmitted as a radio signal over a wireless network. Using a unique code to distinguish each different call, CDMA enables many more people to share the airwaves at the same time - without static, cross-talk or interference. In 1999, the International Telecommunications Union selected CDMA as the industry standard for new "thirdgeneration" (3G) wireless systems. Many leading wireless carriers are now building or upgrading to 3G CDMA networks in order to provide more capacity for voice traffic, along with high-speed data capabilities. feedback formby shaner last modified: 2003-05-22 23:48:41

What is 1x? (#7401)1xRTT is short for single carrier (1x) radio transmission technology, a 3G wireless technology based on the CDMA platform. It is a new Data transfer technology that can give speeds of up to 86kb's per second. This service is unique because instead of being billed by the time spent online, you're actually billed for the amount of data you transfer through the network. This improvement for wireless data is similar to going from dial-up to highspeed service. When data is not being actively transferred, the 1x Data service becomes dormant and a virtual connection to the network is maintained. This , allows you to still receive voice calls or text messages on your cellphone. When you are ready to resume the data session, you can re-engage the network connections immediately. Not only will 1x improve data transfer, it also allows for

more user network capacity and longer battery life. All of Bell Mobility's current phones support the 1x network. 1xRTT is also referred to as CDMA2000. .CDMA vs. TDMAThe CDMA technology used in IS-95 is in technical competition with the TDMA (Time Division Multiple Access) technology used in GSM.

IS-95 by Any Other NameIS-95 is also known as TIA-EIA-95. The original IS-95 CDMA specification is now referred to ascdmaOne.

Newer CDMA StandardsNewer CDMA standards include cdma2000, CDMA 1X EV, CDMA 1XEV-DO, CDMA MC 3X, WCDMA and TD-SCDMA. CDMA-2000 1xRTT is a recent standard for data networking over CDMA-2000 networks.

CDMA Network OperatorsALLTEL, Verizon Wireless , US Cellular, and Qwest communications operate CDMA networks within the United States. Worldwide, there are over 60 million users of IS-95 and other CDMA networks.

Additional Reading on CDMAFor more information on CDMA, visit the CDMA Development Group.

..

Call Setup

Basic Mobile Originating Call Diagram

CDMA2000From Wikipedia, the free encyclopedia

Huawei CDMA2000 EVDO USB wireless modem

CDMA2000 (also known as IMT Multi-Carrier (IMT-MC)) is a family of 3G[1] mobile technology standards, which use CDMA channel access, to send voice, data, and signaling data between mobile phones and cell sites. The set of standards includes: CDMA2000 1X, CDMA2000 EV-DO Rev. 0, CDMA2000 EV-DO Rev. A, and CDMA2000 EV-DO Rev. B[2]. All are approved radio interfaces for the ITU's IMT-2000. CDMA2000 has a relatively long technical history and is backwardcompatible with its previous 2G iteration IS-95 (cdmaOne). In the United States,CDMA2000 is a registered trademark of the Telecommunications Industry Association (TIA-USA)[3]. The successor to CDMA2000 is LTE, part of the competing 3GPP family.[4]Contents[hide]

1 1X 2 1xEV-DO 3 Networks 4 History 5 References 6 External links

[edit]1XCDMA2000 1X (IS-2000), also known as 1x and 1xRTT, is the core CDMA2000 wireless air interface standard. The designation "1x", meaning 1 times Radio Transmission Technology, indicates the same RF bandwidth as IS-95: a duplex pair of 1.25 MHz radio channels. 1xRTT almost doubles the capacity of IS-95 by adding 64 more traffic channels to the forward link,orthogonal to (in quadrature with) the original set of 64. The 1X standard supports packet data speeds of up to 153 kbps with real world data transmission averaging 60100 kbps in most commercial applications.[5] IMT-2000 also made changes to the data link layer for the greater use of data services, including medium and link access control

protocols and QoS. The IS-95 data link layer only provided "best effort delivery" for data and circuit switched channel for voice (i.e., a voice frame once every 20 ms).

[edit]1xEV-DOMain article: Evolution-Data Optimized CDMA2000 1xEV-DO (Evolution-Data Optimized), often abbreviated as EV-DO or EV, is a telecommunications standard for the wireless transmission of data through radio signals, typically for broadband Internet access. It uses multiplexing techniques including code division multiple access (CDMA) as well as time division multiple access (TDMA) to maximize both individual user's throughput and the overall system throughput. It is standardized by 3rd Generation Partnership Project 2 (3GPP2) as part of the CDMA2000 family of standards and has been adopted by many mobile phone service providers around the world particularly those previously employing CDMA networks. It is also used on the Globalstar satellite phonenetwork.[6]

[edit]NetworksSee also: List of CDMA2000 networks The CDMA Development Group states that, as of November 2009, there are 308 operators in 116 countries offering CDMA2000 1X and 1xEV-DO service.[7]

[edit]HistoryThe intended 4G successor to CDMA2000 was UMB (Ultra Mobile Broadband), however in November 2008, Qualcomm announced it was ending development of the technology, favoringLTE instead.[8]

..

CDMACode Division Multiple Access (CDMA) is a radically new concept in wireless communications. It has gained widespread international acceptance by cellular radio system operators as an upgrade that will dramatically increase both their system capacity and the service quality. It has likewise been chosen for deployment by the majority of the winners of the United States Personal Communications System spectrum auctions. It may seem, however, mysterious for those who aren't familiar with it. This site is provided in an effort to dispel some of the mystery and to disseminate at least a basic level of knowledge about the technology. CDMA is a form of spread-spectrum , a family of digital communication techniques that have been used in military applications for many years. The core principle of spread spectrum is the use of noise-like carrier waves, and, as the name implies, bandwidths much wider than that required for simple point-to-point communication at the same data rate. Originally there were

two motivations: either to resist enemy efforts to jam the communications (anti-jam, or AJ), or to hide the fact that communication was even taking place, sometimes called low probability of intercept (LPI). It has a history that goes back to the early days of World War II. The use of CDMA for civilian mobile radio applications is novel. It was proposed theoretically in the late 1940's, but the practical application in the civilian marketplace did not take place until 40 years later. Commercial applications became possible because of two evolutionary developments. One was the availability of very low cost, high density digital integrated circuits, which reduce the size, weight, and cost of the subscriber stations to an acceptably low level. The other was the realization that optimal multiple access communication requires that all user stations regulate their transmitter powers to the lowest that will achieve adequate signal quality. CDMA changes the nature of the subscriber station from a predominately analog device to a predominately digital device. Old-fashioned radio receivers separate stations or channels by filtering in the frequency domain. CDMA receivers do not eliminate analog processing entirely, but they separate communication channels by means of a pseudo-random modulation that is applied and removed in the digital domain, not on the basis of frequency. Multiple users occupy the same frequency band. This universal frequency reuse is not fortuitous. On the contrary, it is crucial to the very high spectral efficiency that is the hallmark of CDMA. Other discussions in these pages show why this is true. CDMA is altering the face of cellular and PCS communication by:

Dramatically improving the telephone traffic capacity Dramatically improving the voice quality and eliminating the audible effects of

multipath fading

Reducing the incidence of dropped calls due to handoff failures Providing reliable transport mechanism for data communications, such as facsimile and

internet traffic

Reducing the number of sites needed to support any given amount of traffic Simplifying site selection Reducing deployment and operating costs because fewer cell sites are needed Reducing average transmitted power

Reducing interference to other electronic devices Reducing potential health risks

Commercially introduced in 1995, CDMA quickly became one of the world's fastest-growing wireless technologies. In 1999, the International Telecommunications Union selected CDMA as the industry standard for new "third-generation" (3G) wireless systems. Many leading wireless carriers are now building or upgrading to 3G CDMA networks in order to provide more capacity for voice traffic, along with high-speed data capabilities. CDMA is a form of Direct Sequence Spread Spectrum communications. In general, Spread Spectrum communications is distinguished by three key elements: 1. The signal occupies a bandwidth much greater than that which is necessary to send the information. This results in many benefits, such as immunity to interference and jamming and multi-user access, which we'll discuss later on. 2. The bandwidth is spread by means of a code which is independent of the data. The independence of the code distinguishes this from standard modulation schemes in which the data modulation will always spread the spectrum somewhat. 3. The receiver synchronizes to the code to recover the data. The use of an independent code and synchronous reception allows multiple users to access the same frequency band at the same time. In order to protect the signal, the code used is pseudo-random. It appears random, but is actually deterministic, so that the receiver can reconstruct the code for synchronous detection. This pseudo-random code is also called pseudo-noise (PN). There are three ways to spread the bandwidth of the signal:

Frequency hopping. The signal is rapidly switched between different frequencies within

the hopping bandwidth pseudo-randomly, and the receiver knows before hand where to find the signal at any given time.

Time hopping. The signal is transmitted in short bursts pseudo-randomly, and the

receiver knows beforehand when to expect the burst.

Direct sequence. The digital data is directly coded at a much higher frequency. The

code is generated pseudo-randomly, the receiver knows how to generate the same code, and correlates the received signal with that code to extract the data. How spread spectrum works:

Spread Spectrum uses wide band, noise-like signals. Because Spread Spectrum signals are noise-like, they are hard to detect. Spread Spectrum signals are also hard to Intercept or demodulate. Further, Spread Spectrum signals are harder to jam (interfere with) than narrowband signals. These Low Probability of Intercept (LPI) and anti-jam (AJ) features are why the military has used Spread Spectrum for so many years. Spread signals are intentionally made to be much wider band than the information they are carrying to make them more noise-like. Spread Spectrum signals use fast codes that run many times the information bandwidth or data rate. These special "Spreading" codes are called "Pseudo Random" or "Pseudo Noise" codes. They are called "Pseudo" because they are not real gaussian noise. Spread Spectrum transmitters use similar transmit power levels to narrow band transmitters. Because Spread Spectrum signals are so wide, they transmit at a much lower spectral power density, measured in Watts per Hertz, than narrowband transmitters. This lower transmitted power density characteristic gives spread signals a big plus. Spread and narrow band signals can occupy the same band, with little or no interference. This capability is the main reason for all the interest in Spread Spectrum today.

//////////////////////.Introduction to CDMAby Michael Hendry

This paper provides an introduction to Code Division Multiple Access (CDMA) communications, covering a Radio Carrier Station (RCS) and a Fixed Subscriber Unit (FSU). This introduction to CDMA proceeds heuristically, we use very little mathematics in developing the theories, and do not assume a deep mathematical or engineering background. If you would like further information on the math and communication theories behind this introduction, please consult the following references: Viterbi, A. CDMA: Principles of Spread Spectrum Communication Addison-Wesley Wireless Communications Series, 1995 Pickholtz, R. L., Schilling, D. L., and Milstein, L. B. Theory of Spread-Spectrum CommunicationsA Tutorial IEEE Trans. Commun., vol. COM30, no. 5, May 1982, pp 855-884. Pickholtz, R. L., Schilling, D. L., and Milstein, L. B. Revisions to Theory of Spread-Spectrum CommunicationsA Tutorial IEEE Trans. Commun., vol. COM32, no. 2, Feb 1984, p