ABSTRACT
CONTENTS 7.1 Introduction ............................................................................................... 133 7.2 Data Access Survey .................................................................................. 135 7.3 Different Ways of Integrating a Wireless Network
with a Cellular Network .......................................................................... 136 7.3.1 Loose Coupling ............................................................................. 136 7.3.2 Tight Coupling .............................................................................. 136
7.4 WLAN over GSM ..................................................................................... 137 7.4.1 Sharing the Abis Interface ........................................................... 138
7.4.1.1 Modifying a Linux Kernel to Offer a Transparent Link to Applications and Routing ........ 138
7.4.1.2 Use of Discontinuous Cross Connectors .................... 140 7.4.2 Overlapping WLAN and GSM Traffic ....................................... 140
7.4.2.1 Quasi Best-Effort Service .............................................. 140 7.4.2.2 Best-Effort Traffic on the Gb Interface ........................ 141 7.4.2.3 Multiplexing of GSM/GPRS and Ethernet
Traffic on the Abis Interface ......................................... 142 7.4.2.4 Simulations, Implementation, and Tests of the
Overlapping WLAN and GSM Traffic Solution ........ 143 7.4.2.5 Quality of E1 Traffic and Ethernet Throughput ........ 149
7.5 Conclusion ................................................................................................. 153 7.6 Recommendations .................................................................................... 154 Acknowledgments ............................................................................................. 155 References ........................................................................................................... 155
The development of telecommunications in Africa has shown tremendous growth over the past few years. However, this development has not been homogeneous. Many major cities in Africa have services equivalent to those
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found in Asia or Europe. Global system for mobile communications (GSM), general packet radio service (GPRS), universal mobile telecommunications systems (UMTS), as well as asymmetric digital subscriber line (ADSL), and wireless IP networks are available. These islands of technology on the African continent are separated by thousands of kilometers of underdeveloped terrain encompassing mountains, grasslands, farms, villages, and deserts, where there is minimal or nonexistent electrical, road, or fixed telecom infrastructure [1]. Most operators are willing to bring telephone and Internet access to these disadvantaged populations, but they are confronted with severe constraints. Some of these are: a lack of basic supporting infrastructure; the theft of material; low densities of customers; potentially low return on investment; and a nonuniform distribution of potential subscribers (i.e., an isolated farm or lodge can potentially generate more income for a cellular operator than a complete village). Despite these obstacles, many rural areas in South Africa and Africa have GSM access. In many cases, networks in these areas are over dimensioned and operators are trying to introduce new services to improve their profitability. On the contrary, potential customers like schools, Internet cafes, village councils, small companies, farms, and dispensaries simply need basic and cost-effective access.
