Systems and methods for controlling audible speech distortion in a GPS-based CDMA wireless network using ATM transport

A technology of wireless network and base station controller, applied in the field of code division multiple access wireless communication network

Inactive Publication Date: 2004-03-31
TELEFON AB LM ERICSSON (PUBL)
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

One disadvantage of this approach is that it frequently introduces audible noise into the speech signal whenever "PSTN time" drifts by 125 microseconds relative to "GPS time"

Method used

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  • Systems and methods for controlling audible speech distortion in a GPS-based CDMA wireless network using ATM transport
  • Systems and methods for controlling audible speech distortion in a GPS-based CDMA wireless network using ATM transport
  • Systems and methods for controlling audible speech distortion in a GPS-based CDMA wireless network using ATM transport

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Embodiment Construction

[0018] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0019] figure 1 An overview of a representative communication network 8 is shown. The network 8 comprises a PSTN 12 connected to a CDMA wireless network 10 . PSTN12 supports PCM voice signal, which is a 64kps digital voice signal sampled at 8KHz frequency. The CDMA network 10 includes an MSC15, a BSC17, an RBS32 and multiple MS35. MSC15 routes PCM voice signals from PSTN12 to BSC17. The BSC 17 compresses the speech signal into speech coded frames of compressed speech data. RBS 32 then modulates the speech encoded frames into a spread spectrum signal and broadcasts the spread spectrum signal to mobile station (MS) 35 .

[0020] BSC17 comprises a first exchange terminal (ET) 20, a media stream board (MSB) 25 connected to the first ET20, a special purpose board (SPB) 30 connected to MSB25 and a second ET27 connected to SPB30. Although a typical BSC17 can support hundreds of MSBs and SPBs, for simplicity, the BSC17 is...

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Abstract

A Base Station Controller (BSC) that reduces the occurrence of audible noise in a Code Division Multiple Access (CDMA) radio network is provided. The BSC according to one embodiment of the present invention comprises a Media Stream Board (MSB) for compressing groups of 160 PCM speech samples from a Public Switch Telephone Network (PSTN) into vocoded frames, and a Special Purpose Board (SPB) for reformatting the vocoded frames from the MSB into over-the-air CDMA vocoded frames. The MSB and SPB each have a local timer that is slave to 'PSTN time'. The BSC further comprises a Timing Unit Board (TUB) connected to a GPS receiver. The TUB receives 'GPS time' from the GPS receiver. The TUB generates timing cells, each containing time-of-day information according 'GPS time'. The TUB distributes the timing cells to the MSB and SPB over an Asynchronous Transfer Mode (ATM) network. The MSB and SPB use the received timing cells to compare their local timer, which tracks 'PSTN time', to 'GPS time'. The MSB and the SPB realign their local timer with 'GPS time' whenever their local timer drifts from 'GPS time' outside of a predetermined time window.

Description

field of invention [0001] The present invention relates generally to Code Division Multiple Access (CDMA) wireless communication networks, and, more particularly, to systems and methods for reducing the occurrence of audible noise in CDMA wireless networks. Background of the invention [0002] A CDMA wireless network provides a communication link between a caller on the public switched telephone network (PSTN) and a caller on a mobile station (MS). The PSTN supports pulse code modulation (PCM) voice signals, which are digital voice signals sampled at a frequency of 8KHz. The CDMA network consists of a base station controller (BSC) for compressing groups of 160 PCM voice samples from the PSTN into 20 ms vocoded frames, and radio base stations (RBS) for The encoded frame is modulated into a spread spectrum signal and the spread spectrum signal is broadcast to MSs. [0003] The RBS broadcasts the spread spectrum modulated frames to the MSs at a specific frame offset time that...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): H04B7/26
CPCH04B7/2628
Inventor D·春M·德斯潘德S·希克斯B·奈特李国钧R·帕拉科德蒂R·拉马斯瓦米G·塞拉纳D·瓦尔克J·张
Owner TELEFON AB LM ERICSSON (PUBL)
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