Browse Prior Art Database

BURST-BY-BURST SIGNALLING IN CELLULAR RADIO SYSTEM

IP.com Disclosure Number: IPCOM000006728D
Original Publication Date: 1993-Mar-01
Included in the Prior Art Database: 2002-Jan-25
Document File: 2 page(s) / 112K

Publishing Venue

Motorola

Related People

Jonathan Withers: AUTHOR

Abstract

A consequence of the increasingly large numbers of subscribers using cellular systems is that cell sizes (the area served by one radio base station) are becoming smaller in order to provide the necessary system capac- ity. Cell sizes below lkm radius are now quite common. The need to perform 'hand-ofP from one cell to another is clearly increased due to the fact that a cell boundary is more likely to be crossed during a call but, in addition, the time in which the hand-off can be effected is reduced.

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INC. Technical Developments Volume18 March 1993

BURSFBY-BURST SIGNALLING IN CELLULAR RADIO SYSTEM

by Jonathan Withers

   A consequence of the increasingly large numbers of subscribers using cellular systems is that cell sizes (the area served by one radio base station) are becoming smaller in order to provide the necessary system capac- ity. Cell sizes below lkm radius are now quite common. The need to perform 'hand-ofP from one cell to another is clearly increased due to the fact that a cell boundary is more likely to be crossed during a call but, in addition, the time in which the hand-off can be effected is reduced.

  From a system control viewpoint, this requires that those mobiles in need of a hand-05 or power adjust- ment must be quickly identified and processed in order to successfully sustain the call in progress. Whilst the GSM system offers far more in the way of measure- ment reports to the network than are provided in cur- rent analogue systems, in microcellular applications the measurement reporting process can be too slow to respond to rapid changes to the mobile station's 'radio environment: This problem is particularly noticeable in PCN systems, where below-roof-top antennas result in sharp changes in signal strength at street comers.

  This invention describes a method by which the mobile station provides additional information to the base station at a much higher sampling rate in order to per- mit more rapid decision making by the network. It is required that the base station has knowledge of this addi- tional capability of the mobile, otherwise the mobile oper- ates according to standard GSM procedures.

  A GSM multi-frame comprises lb4 TDMA frames each transmitted as a burst of data, in which the 13th, 39th, 65th and 91st frames contain control information ("the slow associated control channel-SACCH"). This is illustrated in Figure 1. In order to receive the signal- lmg information on the signal strengths monitored by the mobile, it is necessary to receive all four SACCH frames of a multi-frame, ie. one measurement report is received every 104 frames, which is approximately half a second. In practice, the measurement reports must be further averaged in order to take out short term vari- ability from the measurements. This process may take

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10-15s which is a significant time lag. If the mobile user walks around a comer and suddenly loses his serving signal, there is a considerable period before the system is aware ofwhat has happened and can react.

  This problem is illustrated in Figure 2, in which the signal strength...