Abstract
In this paper, performance enhancement of Wireless Local Loop (WLL) employing Spatial Division Multiple Access (SDMA) with orthogonal CDMA for the quasi-synchronous reverse link is investigated. The static channel characteristic of WLL allows base station adaptive antenna arrays and subscriber directional antenna to be used effectively. We give explicit expressions of the capacity to access their performance. In such an environment, dynamic sectorization is introduced and a simple dynamic spreading code assignment scheme is proposed to assign codes for users in different areas. Simulations results are presented which demonstrate that the use of orthogonal CDMA/SDMA with the proposed dynamic code assignment scheme yields a drastic improvement over using SDMA or orthogonal CDMA alone.
Highlights
There has been a growing interest in deploying Wireless Local Loop (WLL) system to provide wireless telephone services for fixed subscribers, especially in sub-urban areas or developing countries
To achieve a further increase in capacity, Spatial Division Multiple Access (SDMA) can be employed in WLL, since it allows the use of highly directive antenna or adaptive antenna arrays at both base station and subscriber terminals
This is more evident in WLL, since the main shortcoming of CDMA, being the power control error due to fast fading, is largely eliminated
Summary
There has been a growing interest in deploying WLL system to provide wireless telephone services for fixed subscribers, especially in sub-urban areas or developing countries. To achieve a further increase in capacity, SDMA can be employed in WLL, since it allows the use of highly directive antenna or adaptive antenna arrays at both base station and subscriber terminals. CDMA is considered to be providing the highest capacity among other alternatives such as FDMA and TDMA [1]. This is more evident in WLL, since the main shortcoming of CDMA, being the power control error due to fast fading, is largely eliminated. The capacity enhancement of WLL utilizing these two approaches together is investigated. With SDMA, the conventional fixed sectorization is no longer applicable and this invokes the problem of how to assign codes to users in different areas. SYSTEM MODEL 'This work was supported in pan by the Natural Sciences and Engineering Research Council of Canada (NSERC) in the form of scholarship, in pan by the Communications & Information Technology Ontario and in part by Bell Mobility Cellular
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