User Manual

Demand Assignment
System Overview GSI 002
605-0000-450
Draft Issue 1.3dr Date 8/02/00
Page 16 of 16
All signalling is digital using either Channel Associated Signalling (CAS) or Common
Channel Signalling (CCS) protocols. AS4000 DA interfaces to digital switching
systems that have 2Mbit/s subscriber ports.
Support for 2 wire VF interfacing is via external channel bank equipment, such as
Alcatel’s LS-120.
• Channel Associated Signalling. Support for timeslot 16 ABCD bit CAS is provided.
The AS8100 management system allows for flexible configuration of the protocol, to
interface with switches from various manufacturers.
• Common Channel Signalling. V5.1 and V5.2 are supported by AS4000 DA.
Proprietary protocols such as DASS2 and DSS1 may be supported through
appropriate software loads.
• The V5.1 network interface as specified in ETS 300-324-1 is used for the
presentation of traffic at a non-concentrated interface. The V5.1 interface supports
both POTS and ISDN services.
• The V5.2 network interface as specified in ETS 300-347-1 is used for the
presentation of traffic at a concentrated interface. The V5.2 interface supports both
POTS and basic rate ISDN services. The AC supports V5.2 groups of up to 16 E1
links.
• The AC supports dedicated data services using 64kbit/s timeslots. Cross-connect at
the 64 kbit/s level from any input / output port is configurable via the management
system.
7. AS4000 Air Interface
7.1. CDMA Technology
AS4000 uses a radio air-interface, specifically designed for Wireless Fixed Access to
provide high quality, and low delay bearers for telephony, data and ISDN services.
AS4000 uses Direct Sequence Spread Spectrum Code Division Multiple Access (DS-
CDMA) on the air-interface between the CT and STs, allowing multiple radio links to
share the same RF channel. A set of specialised codes are used which are shared
between the ST and its corresponding modem in the CT.
There are two stages to the CDMA modulation / demodulation process. Firstly direct
sequence spreading is performed on each individual radio link by a pseudo-random
noise (PN) code. Then multiple access, where multiple links share the same RF channel,
is achieved by using a set of orthogonal Rademacher - Walsh (RW) codes. The PN and
RW codes are combined into a unique and shared composite code used to modulate and
demodulate each radio link.
AS4000 implements a version of CDMA optimised for fixed access This is significantly
different from other commercial CDMA implementations.