Base Station System (BSS)

INTRODUCTION

The Base Station System (BSS) is responsible for all the radiorelated functions in the system, such as:

• Radio communication with the mobile units

• Handover of calls in progress between cells

• Management of all radio network resources and cell configuration data.

 BSS consists of three components:

• Base Station Controller (BSC):

-The BSC is the central node within a BSS and co-ordinates the actions of TRC’s and RBS’s.

• Transcoder Controller (TRC):

-The TRC provides the BSS with rate adaptation capabilities. This is necessary because the rate used over the air interface and that used by MSC/VLRs are different - 33.8 kbits/s and 64 kbits/s respectively. A device, which performs rate adaptation is called a transcoder.

• Radio Base Station (RBS):

An RBS acts as the interface between MS’s and the network, by providing radio coverage functions from their antennae.

BSS in GSM systems

BASE STATION CONTROLLER AND TRANSCODER CONTROLLER

There two main options available for implementing the TRC and BSC in Ericsson’s BSS:

• BSC/TRC:

A combined BSC and TRC on the same AXE. This is suitable for medium and high capacity applications, e.g. urban and suburban area networks. The node can handle up to 1,020 transceivers (TRXs). 15 remote BSC’s can be supported from one BSC/TRC.

• Stand-alone BSC and stand-alone TRC:

The stand-alone BSC (without transcoders) is optimized for low and medium capacity applications and is a complement to the BSC/TRC, especially in rural and suburban areas. It caters for up to 300 TRX’s. The stand-alone TRC is located at the MSC/VLR to increase transmission efficiency. A stand-alone TRC can support 16 remote BSCs.

TRC utilization and transmission rates in BSS

RADIO BASE STATIONS

 Radio Base Station (RBS) 2000 series of base stations implements the GSM-defined BTS. This includes the following RBS’s:

• RBS 2101

• RBS 2102

• RBS 2103

• RBS 2202

• RBS 2301

• RBS 2302

• RBS 2302 MAXITE

• RBS 2401

OTHER ACCESS NETWORK EQUIPMENT

Many mobile networks include additional equipment to provide improved coverage. Examples of such equipment includes:

• Repeaters:

These are placed in locations throughout the access network to repeat the digital signal from the MS and BTS. This helps to reduce the BER and thus provide better quality calls to subscribers. A typical location for a repeater may be on top of a building

• Leaky cable:

 This is simply a cable carrying the electromagnetic energy,which has “holes” in it to leak out this radio signal at regular intervals. This may be suitable in areas,which are difficult to cover using traditional base station equipment. For example, a leaky cable could be used to provide coverage within an underground train system