Product Info

System Description WipLL Radio Technology - Physical Layer
25030311-08 Airspan Networks Inc. 2-27
2.6.3.1. FDD vs. TDD
Frequency Division Duplex (FDD) interference analysis is relatively simple. The
frequency separation between downlink and uplink (50 to 100 MHz) enables
Airspan to conduct downlink and uplink interference analysis independently.
However, in Time Division Duplex (TDD), since Tx and Rx are not synchronized,
cross-link interference, for example, between a transmitting BSR and an adjacent
receiving BSR, may result. It is expected that these interferences will be dominant in
the TDD mode.
The major consequence of this are the different limitations imposed on frequency
separation between adjacent BSRs:
 FDD: 2 MHz
 TDD: 4 MHz
The required separation is a function of the isolation between co-located antennas.
The 4-MHz separation is based on 60 dB isolation. Based on this, a simple
frequency allocation for a stand-alone cell is presented in Figure 2-6.
Frequency Allocation
Single Cell (FDD)
11
9
7
5
3
1
Frequency Allocation
Single Cell (TDD)
Figure 2-6: Frequency Allocation for a stand-alone cell: FDD (left) vs. TDD (right)