User Manual

AS4000 Wireless Local Loop
System Overview
GSI 001
605-0000-430
Issue 1.2 Date 7/4/99
Page 12 of 16
2.0 2.3 2.5 3.4 3.6 Ghz
– C Band 2.0 - 2.3 GHz
Channel Spacing 3.5 Mhz Duplex Spacing 175Mhz
C1 2028Mhz to 2245Mhz
C2 2045.5Mhz to 2262.5Mhz
C3 2066.5Mhz to 2283.5Mhz
– S Band 2.3 - 2.5 GHz
Channel Spacing 4.0 Mhz Duplex Spacing 94Mhz
S1 2306 Mhz to 2448 Mhz
S3 2338 Mhz to 2480 Mhz
–X Band 3.4 - 3.6 GHz
Channel Spacing 3.5 Mhz Duplex Spacing 100Mhz
X1 Uplink 3411.75 Mhz to 3450.25 Mhz Downlink 3511.75 Mhz to 3550.25Mhz
X2 Uplink 3432.75 Mhz to 3471.25 Mhz Downlink 3532.75 Mhz to 3571.25Mhz
X2 Uplink 3457.25 Mhz to 3495.75 Mhz Downlink 3557.25 Mhz to 3595.75 Mhz
An Airspan
Channel Plan
Frequency Ranges
TX RX
1 12 1 12
C
S
X
Figure 10. Frequency Plans.
9 Code Division Multiple Access (CDMA) Overview
The design of the AS4000 Wireless Fixed Access System (WFAS)equipment incorporates a
number of the latest radio transmission techniques, in addition to the use of digital line-
transmission and inter-node signalling techniques.
Included in the design of the AS4000 WFAS equipment are:
• Spread Spectrum (SS), of the Direct Sequence (DS) type
• Code Division Multiple Access (CDMA)
A brief outline of the principles involved now follows:
9.1 Spread Spectrum
To obtain reliable transmission in noisy radio environments, the transmitted signal is
‘spread’ over a frequency range that is in excess of the minimum bandwidth that would
otherwise be needed. Direct sequence spread spectrum is used in which the message to be
sent is modulated directly with a pseudo-random spreading code. Spreading is achieved by