wireless tech terms

8/2/2019 Wireless Tech Terms

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RF optimization is to optimize radio frequency (RF) signals. RF optimization can

control the pilot pollution and soft handover ratio in the drive test while

optimizing the signal coverage, thus ensuring normal distribution of radio signals

before service parameters are optimized.

Objectives Of RF Optimization:Coverage ratio

95%

Perform test on the acceptance route that should not cover any area without

coverage.

The downlink CPICH Ec/Io of the planned full-coverage service is greater than or

equal to -12 dB and the downlink CPICH RSCP is greater than or equal to -95 dBm.

CPICH Ec/Io -12 dB

95%

Test result from the Scanner, with no service carried outdoors

CPICH RSCP -95 dBm

95%

Test result from the Scanner, with no service carried outdoors

Soft handover ratio

30%-40%

The soft handover ratio in the RF optimization phase should be 5% to 10% lower

than the target value. This is because the later optimization will cause a rise ofsoft handover ratio.

Pilot pollution ratio

5%

Post Processing (Optimization):

Data post-processing, log analysis, failure categorization and weekly reporting

is done offsite.

Optimization is an ongoing process. The goal is to improve quality of

service, retain existing subscribers, and attract new ones while continually

expanding the network.

Optimization process begins with drive-testing, moves to post-processing,

then requires data analysis, and finally action needs to be taken correct the

problems. Drive-testing is performed again to verify that the actions were

effective.


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Drive Tests:

Drive testing is a method of measuring and assessing the coverage,capacity andQuality of Service(QoS) of a mobile radio network.

Advantaged Of Drive Tests:

Less labor intensive and time consuming

More comprehensive, based on large number of users

Not limited to time of test drive

Uplink and Downlink analysis possible

Subscriber behavior mix of outdoor, indoor, incar use

Several functions of drive test:

- Analyzing customer complaint of certain operator in their home or office area

- Finding problem in BTS (Timeslot Check,TRX Check,Swap Feeder)

- Analyzing the result of optimization process (continuity and all of area)

There are softwares can be used for drivetest that installed on laptop. TEMS

Investigation (Ericsson), NEMO (Nokia).

Drive tests are performed to identify problems such as RF coverage Holes, Pilot

pollution, Congestion and capacity problems, missing neighbors, UTRAN

generated failures, Core network failures (CS, PS).

1) RF Coverage Hole:

Coverage hole is an area within the radio coverage footprint of a wireless system

in which the RF signal level is below the design threshold. Coverage holes are

usually caused by physical obstructions such as buildings, foliage, hills, tunnels

and indoor parking garages.

2) Pilot Pollution:

Pilot pollution is a type of co-channel interference in CDMA systems caused when

the pilot code from a distant cell or base station is powerful enough to create an

interference problem.

Causes of Interference:

co-channel interference

adjacent channel interference

intermodulation: mainly on one link only

multipath interference
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------ Antenna down tilt often used to minimize interference.

Cause for Poor Signal Quality:

low signal strength (coverage related)

interference

3) Congestion:

Congestion refers to the situation that the traffic in the network or part of the

network is in excess of network capacity. When congestion happens,

transmission will slow down and some packets may get dropped.

4) UTRAN: UMTS Terrestrial Radio Access Network

UTRAN, short for Universal Terrestrial Radio Access Network, is a collective term

for theNode B's andRadio Network Controllerswhich make up theUMTSradio

access network. This communications network, commonly referred to as 3G (for

3rd Generation Wireless Mobile Communication Technology), can carry many

traffic types from real-timeCircuit SwitchedtoIPbasedPacket Switched. The

UTRAN allows connectivity between theUE(user equipment) and thecore

network. The UTRAN contains the base stations, which are calledNode Bs, and

Radio Network Controllers(RNC).

The RNC provides control functionalities for one or more Node Bs. The RNC
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carries outradio resource management, some of themobility management

functions and is the point where encryption is done before user data is sent to

and from the mobile. A Node B and an RNC can be the same device, although

typical implementations have a separate RNC located in a central office serving

multiple Node Bs. Despite the fact that they do not have to be physically

separated, there is a logical interface between them known as the Iub. The RNC

and its corresponding Node Bs are called theRadio Network Subsystem(RNS).

There can be more than one RNS present in a UTRAN.

There are four interfaces connecting the UTRAN internally or externally to other

functional entities: Iu, Uu, Iub and Iur. The Iu interface is an external interface

that connects the RNC to the Core Network (CN). The Uu is also external,

connecting the Node B with the User Equipment (UE). The Iub is an internal

interface connecting the RNC with the Node B. And at last there is the Iurinterface which is an internal interface most of the time, but can, exceptionally

be an external interface too for some network architectures. The Iur connects

two RNCs with each other.

INTRODUCTION:

Currently in 3GPP the UMTS Terrestrial Radio Access Network (UTRAN) is

conceived as a hierarchical architecture. The Node B is responsible for the

transmission in a cell or a number of cells and the Radio Network Controller

(RNC) manages the resources in the Node Bs and serves as a point oftermination for the user connections.

Node B:

The Node B represents a single point of failure for the cell or group of cells it

controls. When the Node B fails, radio transmissions in its cells become

impossible. This cannot be avoided but is usually reduced by foreseeing spare

boards in the Node B.

In addition, at the edges of the cell, this is sometimes compensated by adjacentcells increasing their coverage.

RNC:

When an RNC fails, however, not only all user connections controlled by this RNC

are dropped, but also the whole area of cells controlled by this RNCs loses its
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transmission capability. The RNC thus represents a single point of failure, with

serious impacts on the UTRAN's capacity in case of breakdown.

KPI Examples:

Call Setup Success Rate (CSSR)

Call Completion Success Rate (CCSR)

Call Setup Time

TCP Throughput

Latency (Round-Trip Time)

Drop Call Rate (DCR)

Handover Success Rate (HOSR)

Test Sequence:

The initial testing is focused to improve the performance of the basic services (CS

voice call and PS data call). The test sequence is later modified to cover any other

available services according to clients request (PS web access, Cs data call, SMS,

MMS, Video call).

Drive Test Measurement (TEMS etc. together with a GPS):

Signal Strength

Co-channel and adjacent interference

Handover relations

Coverage: Analysis for fulfillment of Coverage Requirements (Urban, rural ...

areas, outdoor, in-car, indoor)

Dropped Call: Analysis for Dropped Calls due to Interference, SW/HW failures,

Transmission Network Failures.

Reasons for dropped calls

lack of coverage


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interference problems

handover problems

lack of synchronization in network

problems with other parts of the network

Call Setup: Analysis for Blocking and Capacity Limitations, Analysis for Resource

Allocation Procedures.

Reasons for failed call setups

lack of coverage

database problems

Improper Integration of Nobe B

database inconsistencies

parameter settings, e.g. RXLEV_ACCESS_MIN, RACHBT,

cell reselection related parameters

network congestion

Handover: Analysis for Efficient Handover Performance.

Fine-tuning of handover parametersMoving cell boundaries in order to

Enhance success rate for critical handovers

Minimize local interference at the cell edge

Traffic load sharing between cells

Compared to other optimization measures improvement potential is limited

Affected by

Measurement averaging

Power control parameters

Speech Quality: Analysis for Interference.


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Softer Handover:

The UE is connected to at least 2 cells belonging to the same Node B, the

handover is called Softer Handover, and in this case, the uplink signals from the

different cells are combined in the Node B. Softer handover is a special case of soft handover where the radio links that areadded and removed belong to the same Node B (i.e. the site of co-located base

stations from which several sector-cells are served. In softer handover, macro

diversity with maximum ratio combining can be performed in the Node B,

whereas generally in soft handover on the downlink, macro diversity with

selection combining is applied.

Generally we can distinguish between intra-cell handover and inter-cell

handover. For UMTS the following types of handover are specified:

Handover 3G -3G (i.e. between UMTS and other 3G systems)FDD soft/softer handover

FDD inter-frequency hard handover

FDD/TDD handover (change of cell)

TDD/FDD handover (change of cell)

TDD/TDD handover

Handover 3G - 2G (e.g. handover to GSM)

Handover 2G - 3G (e.g. handover from GSM)

There is a disadvantage (trade-off) between soft handover and system capacity.

A UE involved in Soft/Softer Handover uses several radio links, more DL

channelization codes and more DL power than a single link connection. However,

as long as the number of radio links involved in Soft Handover is optimized, the

capacity advantage offered due to Soft Handover from interference reduction is

larger and hence system capacity is actually improved.

Inter-RAT hard handover:

When UE reaches end of coverage area for UMTS services, it can handover to a

2G service like GSM (if the UE supports multiple RAT). Inter-RAT handover

procedure can be initiated in variety of ways. RNS might send a Handover From

UTRAN command explicitly telling the UE to move to a different RAT or the UE

might select a cell that belongs to a different RAT or the Network may ask UE to

perform Cell Change Order from UTRAN.

Inter-RAT hard handover using Handover from UTRAN command can be

performed when there are no RAB's or when there is atleast one CS domain RAB.

The state of the UE is CELL_DCH.


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Inter-RAT hard handover using Cell change order from UTRAN can be performed

when UE is either in CELL_DCH or CELL_FACH state. The only requirement is that

there should be atleast a PS signaling connection and no CS signaling connection.

Active Set: The cells involved in Soft/Softer Handover and measured by the UE.

Scrambling Code:

Scrambling Codes (SCs) are the internal method used to identify and distinguish

sectors from one another in 3GPP compliant WCDMA networks. Mobile handsets

utilize Scrambling Codes to report to the network about which sectors they are

able to access.

Each transmitter in WCDMA has its unique code named Scrambling Code (SC). In

the DL direction, SC is used to distinguish each cell and in the UL direction SC is

used to distinguish each use (UE). UE detects DL SC using cell search procedure

after slot and frame synchronization process. 3GPP (TS 25.213) has specified 512

Primary Scrambling Code (PSC) that can be used in the network (Actually, total of

218-1 = 262,143 scrambling codes, numbered 0262,142 can be generated.

However not all the scrambling codes are used).512 PSC are divided into 64 SC

Group (SC Group 063) and each cell is allocated one and only one PSC.

SC in DL is assigned based on Planning and SC in UL is assigned automatically bynetwork at call setup phase. DL PSC must be considered in the planning scope to

avoid Co-SC problem that make UE cant distinguish cell correctly due to identical

scrambling codes are detected.

Scrambling code planning is not unique and can be performed in many ways. The

following rules are commonly used in PSC planning:

1. Cell and its neighbors can not use the PSC from the same group

2. We should provide spare PSC to accommodate new node expansion for the

future

3. Different PSC group allocation for each cell type (Macro, Micro and In Building)


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CPICH:

CPICH stands for Common Pilot ChannelinUMTSand some otherCDMA

communications systems.

InWCDMAFDDcellular systems, CPICH is adownlinkchannel broadcast byNode

Bswith constant power and of a known bit sequence. Its power is usually

between 5% and 15% of the total Node B transmit power. Commonly, the CPICH

power is 10% of the typical total transmit power of 43dBm.

Information on W-CDMA CPICH

The W-CDMA CPICH is used in the Scrambling Coding Identification phase of W-

CDMA synchronization to complete the synchronization of the W-CDMA User

Equipment (mobile phone) to the W-CDMA Base Transceiver Station (W-CDMABTS).

What is a typical CPICH power?

CPICH power typically takes about 8~10% of the total Node B power. For a 20W

(43dBm) Node B, CPICH is around 2W (35.1 ~ 33dBm).

In urban areas where in-building coverage is taken care of by in-building

installations, the CPICH may sometimes go as low as 5% because:1) The coverage area is small since users are close to the site, and2) More power can be allocated to traffic channels

Role of CPICH:

CPICH is the reference channel used for cell selection and handover procedures.

1. UE measures the received power of CPICH channel from different cells (called

the Monitored Set) and selects the one with the highest one as the serving cell.

2. The decision to add or remove the Active Set depends on the ratio between

the received CPICH level of the best cell and other cells.
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difference between the signal strength and the noise floor.

What is noise Floor?

The noise floor is the measure of the signal created from the sum of all thenoise

sources and unwanted signals within a measurement system.

Eb/N0=> Bit Energy-to-Noise Density

Bit Energy-to-Noise Density (Eb/N0) is the ratio of bit energy to noise density.

This value is used to specify the lower limit of operation in most digital

communications systems and is also used to measure radio channel performance.

Ec/N0 = Carrier-to-noise Ratio

2G speed range

HSPA+ HSDPA speed Range 20-40 Mbps (2MBPS)

4G 100 Mbps (100mbps/8 = 12.5 MBPS)

Interleaving:

Interleaving is basically a way to arrange data to protect against burst errors,

which happen rarely but can disrupt data transmission when they do occur. Thedownside to having interleaving enabled is that it increases latency (i.e. it slows

down the connection).

What is C/I Ratio?

The Carrier to Interface ratio, or C/I, is the ratio of the amount of power in an RF

carrier to the power of the interference that exists within the channel.

BSIC - Base Station Identity Code:

The Base Station Identity Code (BSIC) is a code used inGSMto uniquely identify

a base station. The code is needed because it is possible that mobile stations

receive thebroadcast channelof more than one base station on the same

frequency. This is due to frequency re-use in acellular network.

The BSIC consists of 6 bits of which the first three identify the network (Network
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Colour Code,NCC). The other 3 bits are used by the operator to uniquely identify

base stations within a certain area.

Frequency Reuse:

Frequency reuse is a technique of reusing frequencies and channels within a

communications system to improve capacity and spectral efficiency. Frequency

reuse is one of the fundamental concepts on which commercial wireless systems

are based that involves the partitioning of an RF radiating area (cell) into

segments of a cell. One segment of the cell uses a frequency that is far enough

away from the frequency in the bordering segment that it does not provide

interference problems. Frequency re-use in mobile cellular systems means that

each cell has a frequency that is far enough away from the frequency in the

bordering cell that it does not provide interference problems. The same

frequency is used at least two cells apart from each other. This practice enables

cellular providers to have many times more customers for a given site license.

AMR:

AMR is Adaptive Multi Rate, which is a audio recording file format for certain

mobile phones. Originally the development of AMR files was from the Ericsson

(Sony Ericsson) team which now has become the widely used mobile extension

on Sony ericsson cell phones such as SE KE 750i.

SQI:

TEMS products offer the quality measure SQI (Speech Quality Index) for

estimating the downlink speech quality in a GSM, WCDMA, or CDMA cellular

network as perceived by a human listener. Ericsson has developed SQI.

Computing SQI for GSM and WCDMA requires data collected with Sony Ericsson

phones. SQI for CDMA can be based on data from any CDMA phone that is

connectable in TEMS Investigation.

SACCH:The GSM Slow Associated Control Channel - which allows for controlinformation to be exchanged between the MS and the network during a call.

Contrast FACCH.

An auxiliary control channel appended to the traffic channel used by the mobile

station for reporting received signal strength indicator and signal quality

measurements.
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FACCH:

Fast associated control channel - FACCH is a logical channel on a digital traffic

channel that is typically used to send urgent signaling control messages (such as a

handoff or power control message). The FACCH channel sends messages by

replacing speech data with signaling data for short periods of time. In GSM two

special reserved bits are used to inform the receiving device if the data in the

current time slot is digitally coded subscriber traffic or alternatively a FACCH

message. In IS-136 systems, a FACCH message is distinguished from digitally

coded subscriber traffic because two different types of error protection coding

are used for the two types of information.

FER:

Frame error rate (FER), i.e. the percentage of frames that are lost on their way to

the receiving party, usually because of bad radio conditions.

BER:

The BER is simply a percentage of the number of bits it receives that did not pass

error checking.

Signal Strength:

The first and arguably most important consideration in radio link management is

signal strength. In GSM (and most other RF communications) the standard

measure of signal strength is dBm (decibelsin milliwatts). The term received

signal strength indicator(RSSI) is often used but in GSM the term received-signal

level(RXLEV) is preferred. The distinction is that the term RSSI was generally used

on analog networks and RXLEV is used on digital networks. On this website RSSI

will be used for general reference to signal strength and RXLEV for the actual

value that is passed over the network.

RXLEV:

RXLEV is a number from 0 to 63 that corresponds to a dBm value range. 0

represents the weakest signal and 63 the strongest.

RSSI below -110 dBm are generally considered unreadable in GSM. RSSI in the

area of -50 dBm are rarely seen and would indicate that the MS is right next to

the BTS. The main factor that affects RSSI is distance from the tower. However,

other factors such as terrain, elevation, and large objects such as buildings can

dampen signal strength.
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RXQUAL

Although a strong RSSI is desirable, it does not guarantee a quality signal.

RXQUAL is a value that represents the quality of the received signal. The MS

determines the Bit Error Rate (BER) of the signal and reports it back to the

network. The BER is simply a percentage of the number of bits it receives that

did not pass error checking. The bits may have been garbled along the RF path or

lost due to fading or interference. The higher the BER the lower the signal quality.

RXQUAL is given as a number from 0 to 7 and represents a percentage range of

BER.

RxQual is used in GSM and is a part of the Network Measurement Reports

(NMR).[1]

This is an integer the value of which can be between 0 and 7 and reflects thequality of voice. 0 is the best quality, 7 is the worst.

Cell Selection and Reselection

Cell selection refers to the initialregistration that a MS will make with a network.

This normally only occurs when the phone powers up or when the MS roams

from one network to another.

Cell reselection refers to the process of a MS choosing a new cell to monitor once

it has already registered and is camped on a cell. It is important to distinguish

that selection and reselection are done by the MS itself and not governed by the

network. The network would only be responsible for this function when the MS isin aTraffic Channel (TCH). When the MS reselects a new cell it will not inform the

network that it has done so unless that new cell is in a newLocation Area (LA).

There are many parameters involved in selection and reselection of a new cell.

The MS must ensure it is getting the best signal and the network must ensure

that the MS does not cause unneeded strain on the network by switching cells

when unnecessary or undesired.

C1:

C1 is the path-loss parameter that is used to determine the strongest cell for

selection. The MS will calculate a C1 for each tower it can see and select the cell

tower with the highest C1. The C1 uses the following parameters for calculation:

The formula for calculating C1 is given as:C1 = (A) - Max(B,0)where:A =
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(RXLEV - RLAM)B = MS Transmit Power Max CCH -Max RF Output of MSAt first this may seem complicated but if we examine the various parameters and

how they affect the C1 score then it becomes more clear.

A - This value is merely a dB value for the difference between what RSSI is

required to select that cell and what signal strength the MS sees the tower at. If

the RLAM is -110dB and the MS sees the tower at -90dB then the value of A is

20dB. The higher the value of A the higher the C1 and the more attractive this

tower will be to the MS.

B - Just because a MS can receive a tower's signal does not mean that the MS has

enough power to reach that tower. The tower tells the MS what maximum power

level that the MS may use to transmit to that tower. If the phone is capable of

transmitting at this power than there is no problem. However, what if the phonecan not transmit at that power level? The signal from the MS may not have

enough power to reach the tower. Any lack in transmitting power of the MS must

be taken into account when calculating C1. B is essentially the value of this

difference. Let's say a cell tower requires the MS to be able to transmit at a 30dB

power level but this MS is only capable of transmitting at 26dB. In this case the

value of B would be 4dB. This value is subtractedfrom the value of A which has

the result of lowering the value of C1. If the MS is capable of transmitting at the

required power or higher then B will be zero and no adjustments to C1 will be

made.

In summary, the two main factors in determining C1 are the strength of the

received signal and the transmission power the MS is capable of. C1 alone is only

used for cell selection. When a MS is already camped on a cell and it wants to

move to another cell it will reselectit. Cell reselection uses a different criteria C2.

C2:

C2 is the parameter used for cell reselection. Once a MS is camped on a cell it will

continuously monitor the strength of neighbor cells. EveryBCCHsends out aBCCH Allocation (BA) List. This is a list of neighbor cells (ARFCNs) that the MS

must monitor while camped on a particular cell. The MS will monitor these

ARFCNs for signal strength and only reselect a cell that is on this list. The MS will

calculate a C2 value for each cell on the BA list. The cell tower with the highest C2

wins and the MS will move to that cell and camp on it. Keep in mind the C2 is

calculated by the MS and the MS decides which cell tower to camp on. The cell
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that the MS camps on is known as the serving cell. As long as the losing cell and

the gaining cell are both in the sameLocation Areathe MS will not notify the

network that is is selecting a new cell. The MS only needs to notify the network if

it is reselecting the cell that is in a new location area in which case it will do a

location update.

The C2 is calculated using the following parameters:The formula for calculating C2 is:

C2 = C1 + CRO - (Temp_Offset * H)

H = 1 if the MS has been monitoring a particular cell for less than the penalty

time.H = 0 if the MS has been monitoring the particular cell for longer than thepenalty time.H = 0 if the particular cell is the serving cell (the one the MS iscurrently camped on).Let's look at an example to see how the temporary offset works. The following

chart shows two example cell towers and values for C1 and C2 parameters. The

time progresses as the MS moves away from cell A and towards cell B. For sake of

simplicity, we are assuming that the MS can transmit at the max power allowed

and that neither cell is using CRO.

0 seconds - The MS is camped on cell A. The MS calculates the C2 value as 38.

Since the RXLEV for cell B is not above the RLAM the C1 (and C2) are below 0. A

MS will not select a cell with a C1 below 0 and it will not reselect a cell with a C2

below 0.

10 seconds - The RXLEV for cell B meets the minimum threshold (RLAM). The MS

starts a timer as soon as it puts it on its strongest neighbor list. The penalty time

for cell B is 40 seconds, so for the first 40 seconds that cell B is on the strongest

neighbor list it will apply the temporary offset to the C2 value. After including theoffset, the C2 for cell B is -20 dBm.

20 seconds - The C2 for cell A continues to drop as the C2 for cell B continues to

rise. With a C2 of 25, cell A is still the most attractive.

30 seconds - Cell A drops to a C2 of 21 and cell B has a C2 of -5.
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40 seconds - Cell A drops to a C2 of 18. Cell B rises to a C2 of 3. Notice here that if

it were not for the temporary offset, the C2 for cell B would be at 23. At this point

the MS would normally reselect cell B. However, due to the temporary offset, cell

A is still the most attractive.

50 seconds - At this point the penalty time for cell B has expired and the

temporary offset is no longer applied. The C2 for cell B raises from 3 to 27. The C2

for cell B wins over the C2 for cell A and the MS reselects cell B.

The temporary offset would be used if the network wanted to discourage mobile

stations from reselecting a cell as soon as the MS saw it. This is commonly found

in pico-cells. This forces a MS to be in the area of the cell for a certain period

before reselecting it. It prevents mobile stations that just happen to be passing by

from reselecting the cell. In order to reselect the cell, the MS must be in the areafor a certain period of time or be close enough that the RXLEV overcomes the

negative offset value.

Cell Reselection Offset (CRO) - CRO is a value from 0 to 63. Each step represents

a 2 dBm step (0 to 126 dBm). This value is added to C1. A higher CRO value will

make the cell tower more attractive to the MS. The higher the CRO, the more

attractive the cell will be. The network might assign a CRO value to a cell if the

network wanted to encourage mobile stations to utilize that cell. The network

might want to do this in order to reduce the load on other cells during times of

high traffic volume or to force MS's to a certain band.

Neighbor List - The neighbor list is a list of the 6 strongest cells that the MS can

see. The RXLEV for these cells is transmitted in a measurement report from the

MS to the BTS on the SACCH whenever the MS has been allocated an SDCCH or a

TCH. The BSC and MSC use these measurements to determine if the MS needs to

move to a different cell. Whenever a cell is in an active SDCCH or TCH the

network will always manage the handoff. The MS will only move from one cell to

another by itself when it is in idle mode.

Cell Reselection Hysteresis (CRH)

When a MS reselects a new cell it does not need to notify the network unless that

new cell is in a differentLocation Area. When a MS moves into a new location

area it must do alocation updatewhich generates signal messaging between the

BTS, BSC, MSC, VLR, and HLR. If a MS is located along the border of two location
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formula Channel Number = Frequency * 5

BAND & CHANNEL:

A "band" refers to a small portion of the radio spectrum such as the UHF

TV band (470MHz to 860MHz). A "channel" refers to a portion of a bandwhich in the case of the TV Band is around 8MHz wide.

CDMA:

One of the basic concepts in data communication is the idea of allowing

several transmitters to send information simultaneously over a single

communication channel. This allows several users to share a band of

frequencies (seebandwidth). This concept is calledmultiple access.

CDMA employsspread-spectrumtechnology and a special coding scheme

(where each transmitter is assigned a code) to allow multiple users to be

multiplexed over the same physical channel. By contrast,time division

multiple access(TDMA) divides access bytime, whilefrequency-division

multiple access(FDMA) divides it byfrequency. CDMA is a form ofspread-

spectrumsignalling, since the modulated coded signal has a much higher

data bandwidththan the data being communicated.

CDMA (Code-Division Multiple Access) refers to any of severalprotocols used in so-called second-generation (2G) and third-

generation (3G)wirelesscommunications. As the term implies,

CDMA is a form ofmultiplexing, which allows numerous signals to

occupy a single transmissionchannel, optimizing the use of

availablebandwidth. The technology is used in ultra-high-

frequency (UHF)cellular telephonesystems in the 800-MHzand

1.9-GHz bands.

CDMA employs analog-to-digital conversion (ADC) in combination

withspread spectrumtechnology. Audio input is first digitized

into binary elements. The frequency of the transmitted signal is

then made to vary according to a defined pattern (code), so it can
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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, which enhances privacy and makes

cloning difficult.

The CDMA channel is nominally 1.23 MHz wide. CDMA networks

use a scheme calledsoft handoff, which minimizes signal breakup

as a handset passes from one cell to another. The combination of

digital and spread-spectrum modes supports several times as

many signals per unit bandwidth as analog modes. CDMA is

compatible with other cellular technologies; this allows for

nationwide roaming.

The original CDMA standard, also known asCDMA Oneand still

common in cellular telephones in the U.S., offers a transmission

speed of only up to 14.4Kbpsin its single channel form and up to

115 Kbps in an eight-channel form.CDMA2000and Wideband

CDMA deliver data many times faster.

TDMA:

Time division multiple access (TDMA) is achannel access methodforshared medium networks. It allows several users to share the samefrequency channelby dividing the signal into different time slots. The userstransmit in rapid succession, one after the other, each using its own timeslot. This allows multiple stations to share the same transmission medium(e.g. radio frequency channel) while using only a part of itschannelcapacity. TDMA is used in the digital2Gcellular systemssuch asGlobal

System for Mobile Communications(GSM),IS-136,Personal DigitalCellular(PDC) andiDEN, and in theDigital Enhanced CordlessTelecommunications(DECT) standard forportable phones. It is also usedextensively insatellitesystems,combat-net radiosystems, andPONnetworks for upstream traffic from premises to the operator. For usage ofDynamic TDMA packet mode communication, see below.
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FDMA:

Frequency Division Multiple Access or FDMA is achannel access

methodused in multiple-access protocols as a channelization protocol.

FDMA gives users an individual allocation of one or severalfrequencybands, orchannels. It is particularly commonplace insatellite

communication. FDMA, like other Multiple Access systems, coordinates

access between multiple users. Alternatives includeTDMA,CDMA, or

SDMA. These protocols are utilized differently, at different levels of the

theoreticalOSI model.

Disadvantage:Crosstalkmay cause interference among frequencies anddisrupt the transmission.

WCDMA:

W-CDMA (WidebandCode Division Multiple Access), UMTS-FDD,

UTRA-FDD, orIMT-2000CDMA Direct Spread is anair interface

standard found in3Gmobile telecommunicationsnetworks. It is the basis

of Japan'sNTT DoCoMo'sFOMAservice and the most-commonly used

member of theUMTSfamily and sometimes used as a synonym for

UMTS.[1] It utilizes theDS-CDMAchannel access method and theFDD

duplexing method to achieve higher speeds and support more users

compared to mosttime division multiple access(TDMA) schemes used

today.

While not an evolutionary upgrade on the airside, it uses the samecorenetworkas the2GGSMnetworks deployed worldwide, allowing dual-modeoperation along with GSM/EDGE; a feat it shares with other members ofthe UMTS family.

W-CDMA is a spread-spectrum modulation technique; one which uses channelswhose bandwidth is much greater than that of the data to be transferred. Instead

of each connection being granted a dedicated frequency band just wide enoughto accommodate its envisaged maximum data rate, W-CDMA channels share amuch larger band.The modulation technique encodes each channel in such a way that a decoder,knowing the code, can pick out the wanted signal from other signals using thesame band, which simply appear as so much noise.

UMTS uses a core network derived from that of GSM, ensuring backward

compatibility of services and allowing seamless handover between GSM access
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annel_access_method


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technology and W CDMA.

Frequency-Division Duplexing

Frequency-division duplexing (FDD) means that thetransmitterand

receiveroperate at differentcarrier frequencies. The term is frequently

used inham radiooperation, where an operator is attempting to contact a

repeaterstation. The station must be able to send and receive a

transmission at the same time, and does so by slightly altering the

frequency at which it sends and receives. This mode of operation is

referred to as duplex modeor offset mode.

Uplink and downlink sub-bands are said to be separated by the frequency

offset. Frequency-division duplexing can be efficient in the case of

symmetric traffic. In this case time-division duplexing tends to waste

bandwidthduring the switch-over from transmitting to receiving, has

greater inherentlatency, and may require more complexcircuitry.

Another advantage of frequency-division duplexing is that it makes radioplanning easier and more efficient, since base stations do not "hear" eachother (as they transmit and receive in different sub-bands) and thereforewill normally not interfere with each other.

Time-division duplexing

In this duplex method, uplink and downlink transmissions are carried

over the same frequency band by using synchronized time intervals.

Thus time slots in a physical channel are divided into transmission and

reception part.

Time-Division Duplex (TDD) is the application oftime-division

multiplexingto separate outward and return signals. It emulates full duplex

communication over a half duplex communication link.

Time division duplex has a strong advantage in the case where there is

asymmetryof theuplinkanddownlinkdata rates. As the amount of uplink

data increases, more communication capacity can be dynamically

allocated, and as the traffic load becomes lighter, capacity can be taken
http://en.wikipedia.org/wiki/Transmitterhttp://en.wikipedia.org/wiki/Transmitterhttp://en.wikipedia.org/wiki/Transmitterhttp://en.wikipedia.org/wiki/Receiver_(radio)http://en.wikipedia.org/wiki/Receiver_(radio)http://en.wikipedia.org/wiki/Frequencyhttp://en.wikipedia.org/wiki/Frequencyhttp://en.wikipedia.org/wiki/Frequencyhttp://en.wikipedia.org/wiki/Amateur_radiohttp://en.wikipedia.org/wiki/Amateur_radiohttp://en.wikipedia.org/wiki/Amateur_radiohttp://en.wikipedia.org/wiki/Repeaterhttp://en.wikipedia.org/wiki/Repeaterhttp://en.wikipedia.org/wiki/Bandwidth_(signal_processing)http://en.wikipedia.org/wiki/Bandwidth_(signal_processing)http://en.wikipedia.org/wiki/Laghttp://en.wikipedia.org/wiki/Laghttp://en.wikipedia.org/wiki/Laghttp://en.wikipedia.org/wiki/Circuitryhttp://en.wikipedia.org/wiki/Circuitryhttp://en.wikipedia.org/wiki/Circuitryhttp://en.wikipedia.org/wiki/Time-division_multiplexinghttp://en.wikipedia.org/wiki/Time-division_multiplexinghttp://en.wikipedia.org/wiki/Time-division_multiplexinghttp://en.wikipedia.org/wiki/Time-division_multiplexinghttp://en.wikipedia.org/wiki/Asymmetryhttp://en.wikipedia.org/wiki/Asymmetryhttp://en.wikipedia.org/wiki/Telecommunications_linkhttp://en.wikipedia.org/wiki/Telecommunications_linkhttp://en.wikipedia.org/wiki/Telecommunications_linkhttp://en.wikipedia.org/wiki/Downlinkhttp://en.wikipedia.org/wiki/Downlinkhttp://en.wikipedia.org/wiki/Downlinkhttp://en.wikipedia.org/wiki/Downlinkhttp://en.wikipedia.org/wiki/Telecommunications_linkhttp://en.wikipedia.org/wiki/Asymmetryhttp://en.wikipedia.org/wiki/Time-division_multiplexinghttp://en.wikipedia.org/wiki/Time-division_multiplexinghttp://en.wikipedia.org/wiki/Circuitryhttp://en.wikipedia.org/wiki/Laghttp://en.wikipedia.org/wiki/Bandwidth_(signal_processing)http://en.wikipedia.org/wiki/Repeaterhttp://en.wikipedia.org/wiki/Amateur_radiohttp://en.wikipedia.org/wiki/Frequencyhttp://en.wikipedia.org/wiki/Receiver_(radio)http://en.wikipedia.org/wiki/Transmitter


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away. The same applies in the downlink direction.

For radio systems that aren't moving quickly, another advantage is that theuplink and downlink radio paths are likely to be very similar. This meansthat techniques such asbeamformingwork well with TDD systems.

OFDM:

Orthogonal frequency-division multiplexing (OFDM), essentiallyidentical to coded OFDM (COFDM) and discrete multi-tone modulation(DMT), is afrequency-division multiplexing(FDM) scheme used as adigital multi-carriermodulationmethod. A large number of closely-spacedorthogonalsub-carriersare used to carrydata. The data is divided intoseveral parallel data streams or channels, one for each sub-carrier. Each

sub-carrier is modulated with a conventional modulation scheme (such asquadrature amplitude modulationorphase-shift keying) at a lowsymbolrate, maintaining total data rates similar to conventional single-carriermodulation schemes in the same bandwidth.

OFDM is a combination of modulation and multiplexing. Multiplexing generally

refers to independent signals, those produced by different sources. So it is a

question of how to share the spectrum with these users. In OFDM the question of

multiplexing is applied to independent signals but these independent signals are

a sub-set of the one main signal. In OFDM the signal itself is first split into

independent channels, modulated by data and then re-multiplexed to create theOFDM carrier.

OFDM is a special case of Frequency Division Multiplex (FDM). As an analogy, a

FDM channel is like water flow out of a faucet, in contrast the OFDM signal is like

a shower. In a faucet all water comes in one big stream and cannot be sub-

divided. OFDM shower is made up of a lot of little streams.

Modulation - a mapping of the information on changes in the carrier phase,

frequency or amplitude or combination.

Multiplexing - method of sharing a bandwidth with other independent data

channels.

Poor CoverageConcept: The RSCP of pilot signals in the coverage area is smaller than -95

dBm.
http://en.wikipedia.org/wiki/Beamforminghttp://en.wikipedia.org/wiki/Beamforminghttp://en.wikipedia.org/wiki/Beamforminghttp://en.wikipedia.org/wiki/Frequency-division_multiplexinghttp://en.wikipedia.org/wiki/Frequency-division_multiplexinghttp://en.wikipedia.org/wiki/Frequency-division_multiplexinghttp://en.wikipedia.org/wiki/Modulationhttp://en.wikipedia.org/wiki/Modulationhttp://en.wikipedia.org/wiki/Modulationhttp://en.wikipedia.org/wiki/Orthogonality#Communicationshttp://en.wikipedia.org/wiki/Subcarrierhttp://en.wikipedia.org/wiki/Subcarrierhttp://en.wikipedia.org/wiki/Subcarrierhttp://en.wikipedia.org/wiki/Datahttp://en.wikipedia.org/wiki/Datahttp://en.wikipedia.org/wiki/Datahttp://en.wikipedia.org/wiki/Quadrature_amplitude_modulationhttp://en.wikipedia.org/wiki/Quadrature_amplitude_modulationhttp://en.wikipedia.org/wiki/Phase-shift_keyinghttp://en.wikipedia.org/wiki/Phase-shift_keyinghttp://en.wikipedia.org/wiki/Phase-shift_keyinghttp://en.wikipedia.org/wiki/Symbol_ratehttp://en.wikipedia.org/wiki/Symbol_ratehttp://en.wikipedia.org/wiki/Symbol_ratehttp://en.wikipedia.org/wiki/Symbol_ratehttp://en.wikipedia.org/wiki/Symbol_ratehttp://en.wikipedia.org/wiki/Symbol_ratehttp://en.wikipedia.org/wiki/Phase-shift_keyinghttp://en.wikipedia.org/wiki/Quadrature_amplitude_modulationhttp://en.wikipedia.org/wiki/Datahttp://en.wikipedia.org/wiki/Subcarrierhttp://en.wikipedia.org/wiki/Orthogonality#Communicationshttp://en.wikipedia.org/wiki/Modulationhttp://en.wikipedia.org/wiki/Frequency-division_multiplexinghttp://en.wikipedia.org/wiki/Beamforming


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Cross CoverageConcept: The area covered by a BTS exceeds the planned scope and

discontinuous dominant areas are formed in the areas covered by other BTSs.

wireless tech terms

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