WhyTelecom - BSS - BASE STATION SUBSYSTEM

SIGNALING CHANNEL - GSM RADIO INTERFACE

9797 — Tue, 04 Aug 2009 23:30:10 +0000

GSM RADIO CONCEPTS

What are the Allowed Logical channel combinations in GSM

Wed, 15 Jul 2009 05:01:05 +0000

The multiplexing rules of GSM 05.02 allow only certain combinations of logical channels to share a physical channel. The most common combinations are:

Combination I: TCH/F + FACCH/F + SACCH. This combination is used for full rate traffic. It can be used anywhere but C0T0.

Combination II: TCH/H + FACCH/H + SACCH. This combination is used for half rate traffic when only one channel is needed. It can be used anywhere but C0T0.

Combination III: 2 TCH/H + 2 FACCH/H + 2 SACCH. This combination is used for half rate traffic. It can be used anywhere but C0T0.

What is RACH Random Access Channel (RACH)

Wed, 15 Jul 2009 04:55:48 +0000

Random Access Channel (RACH) is used in mobile phones or other wireless device on a TDMA-based network when it needs to get the attention of a base station in order to initially synchronize its transmission with the base station.

Random Access Channel is a shared channel that is used by Wireless Access terminals to Access the Access Network(TDMA/FDMA,and CDMA based network) especially for initial Access and Bursty data transmission.

A key feature of a Random Access Channel is that messages are not scheduled (compared to for example a "Dedicated Channel" in UMTS, that is assigned exclusively to one user at a time). There is no certainty, that only a single device makes a connection attempt at one time, and collisions can result.

What is BCCH - Broadcast control channel

Wed, 15 Jul 2009 04:45:53 +0000

The broadcast control channel (BCCH) is a point to multipoint, unidirectional (downlink) channel used in the Um Interface of a GSM cellular standard. The BCCH carries a repeating pattern of system information messages that describe the identity, configuration and available features of the BTS. These messages also provide a list of ARFCNs used by neighboring BTSs. This message pattern is synchronized to the BTS frame clock by rules defined in GSM Specification 05.02 Section 6.3.1.3. The minimum BCCH message set is system information messages 1-4, although other messages are normally present. The messages themselves are described in GSM Specification 04.08 Sections 9.1.31-9.1.43.