Node BFrom Wikipedia, the free encyclopedia

BTS & Node B antenna mounted on the church tower, Sopot, Poland

Node B is a term used in UMTS equivalent to the BTS (base transceiver station) description used in GSM. It is

the hardware that is connected to the mobile phone network that communicates directly with mobile handsets.

In contrast with GSM base stations, Node B uses WCDMA/TD-SCDMA as the air interface technology. As in all

cellular systems, such as UMTS and GSM, the Node B contains radio frequencytransmitter(s) and the

receiver(s) used to communicate directly with mobile devices, which move freely around it. In this type of

cellular network, the mobile devices cannot communicate directly with each other but have to communicate

with the Node B. [1]

Contents

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1 Functionality

2 Differences between a Node B and a GSM base station

o 2.1 Frequency use

o 2.2 Power requirements

3 Node B setup

4 See also

Functionality

Traditionally, the Node Bs have minimum functionality, and are controlled by an RNC (Radio Network

Controller). However, this is changing with the emergence of High Speed Downlink Packet Access (HSDPA),

where some logic (e.g. retransmission) is handled on the Node B for lower response times.

Differences between a Node B and a GSM base station

Frequency use

The utilization of WCDMA technology allows cells belonging to the same or different Node Bs and even

controlled by different RNC to overlap and still use the same frequency (in fact, the whole network can be

implemented with just one frequency pair). The effect is utilized in soft handovers.

Power requirements

Since WCDMA often operates at higher frequencies than GSM (2100MHz as opposed to 900MHz for GSM),

the cell radius can be considerably smaller for WCDMA than for GSM cells as the path loss is frequency

dependant. WCDMA now has networks operating in the 850-900MHz band. In these networks, at these

frequencies, the coverage of WCDMA is considered better than that of the equivalent GSM network.

Unlike in GSM, the cells' size is not constant (a phenomenon known as "cell breathing"). This requires a larger

number of Node Bs and careful planning in 3G (UMTS) networks. Power requirements on Node Bs and user

equipment (UE) are much lower.

Node B setup

A full setup contains a cabinet, an antenna mast and actual antenna. An equipment cabinet contain e.g. power

amplifiers, digital signal processors and back-up batteries. What you can see by the side of a road or in a city

center is just an antenna. However, the tendency nowadays is to camouflage the antenna (paint it the color of

the building or put it into an RF-transparent enclosure). Smaller indoor solutions may have a built-in antenna on

the cabinet door.

A Node B can serve several cells, also called sectors, depending on the configuration and type of antenna.

Common configuration include omni cell (360°), 3 sectors (3x120°) or 6 sectors (3 sectors 120° wide

overlapping with 3 sectors of different frequency).

Soft handoverFrom Wikipedia, the free encyclopedia

Soft handover or soft handoff refers to a feature used by the CDMA and WCDMA standards, where a cell

phone is simultaneously connected to two or more cells (or cell sectors) during a call. If the sectors are from the

same physical cell site (a sectorised site), it is referred to as softer handoff. This technique is a form of mobile-

assisted handover, for IS-95/CDMA2000 CDMA cell phones continuously make power measurements of a list

of neighboring cell sites, and determine whether or not to request or end soft handover with the cell sectors on

the list.

Due to the properties of the CDMA signaling scheme, it is possible for a CDMA phone to simultaneously

receive signals from two or more radio base stations that are transmitting the same bit stream(using different

transmission codes) on the different physical channels in the same frequency bandwidth. If the signal power

from two or more radio base stations is nearly the same, the phone receiver can combine the received signals

in such a way that the bit stream is decoded much more reliably than if only one base station were transmitting

to the subscriber station. If any one of these signals fades significantly, there will be a relatively high probability

of having adequate signal strength from one of the other radio base stations.

On the uplink (phone-to-cell-site), all the cell site sectors that are actively supporting a call in soft

handover send the bit stream that they receive back to the Radio Network Controller (RNC), along with

information about the quality of the received bits. The RNC examines the quality of all these bit streams and

dynamically chooses the bit stream with the highest quality. Again, if the signal degrades rapidly, the chance is

still good that a strong signal will be available at one of the other cell sectors that is supporting the call in soft

handover.

Soft handover results in a diversity gain called soft handover gain.

Cell breathing (telephony)From Wikipedia, the free encyclopedia

In CDMA-based mobile telephone systems, the effect of radio interference from other

mobile transmitters in the same cell or coverage area is very marked and has a special

name, cell breathing.[1]

The service area of a cell may vary due to interference from transmitting systems, both

within and around that cell. This is true especially in CDMA based systems. The receiver

requires a certain signal-to-noise ratio. As the receiver moves away from the transmitter, the

power transmitted is reduced. As the interference (noise) rises above the received power

from the transmitter, and the power of the transmitter cannot be increased any more, the

signal becomes corrupted and eventually unusable.

The existence of greater cell breathing in CDMA systems complicates their planning, and

requires more Node Bs to be deployed.

OneBase® Base Station System

 OneBase® Pico Node B

OneBase Pico Node B is a fully self-contained WCDMA Node B radio base station that supports 1700, 1900, or 2100 MHz bands. This single carrier picocell wireless base station provides 250 mW power output, features a capacity of up to 80 users, and at 6 kg (13 lb) in weight is easily deployed by a single technician.

The Pico Node B can be deployed in a number of capacity configurations, depending on operator needs. It offers network flexibility because it is fully enabled to support HSDPA high data rate services. It can be reconfigured to interconnect with either E1/T1/J1, STM-1, or Ethernet transmission bearers.

The one-carrier OneBase Pico Node B is the first in a family of small WCDMA base stations being developed by Andrew. The OneBase Micro is a complete microcell wireless base station with one- or two-carrier operation and HSPDA capability.

Units complement any OEM’s existing product range and look, so the OneBase Pico BTS can be offered as part of a product portfolio without committing internal development resources. Time to market is reduced, and both risk and cost are reduced.

Key benefits:

Low cost and ease of deployment Full O&M support Solves key network challenges

o Provides high capacity spot coverageo Limits the impact of hot spots on macro network planning assumptionso Prevents “pilot signal pollution” problems in high rise buildingso Can prevent large numbers of users in soft handover status requiring high

processing capacityo Offers flexible deployment scenarios to meet in-building needs