Cellular Wireless Communication
Cellular communication architecture is the turning point in wireless communication technologies based on the concept of spatial multiplexing. The three major problems in planning spatial multiplexing are: (i) elimination of interference, (ii) increasing c
- PDF / 833,997 Bytes
- 34 Pages / 439.37 x 666.142 pts Page_size
- 36 Downloads / 238 Views
Cellular Wireless Communication
2.1 Introduction Originally, the focus of mobile radio systems design was towards increasing the coverage of a single transceiver. A single powerful base station was employed to provide connectivity to all mobile devices in a service area. Since spectrum length allocated for private communication is limited, it led to spectral congestion in the service area when large number of mobile clients became concurrently active. Typically, in radio communication system, a user requires about 30 kHz for voice communication. Therefore, if a high power antenna is mounted on a large tower to cover an entire town, it can support just about 25 MHz/30 kHz = 833 users, assuming that 25 MHz spectral band is available for private communication. An obvious way to get around the technical limitations and increase both the capacity and coverage is to reuse allocated frequencies without interferences. The idea was driven by a simple counter thought to the use of high powered transceiver. When a limited range transceiver is used then the wireless connectivity can be provided only in a small finite area of few hundred square meters. However, the frequency of an already deployed transceivers can now be reused by deploying another similar transceiver at a distance where the new transceiver does not interfere with the transceivers which were deployed earlier. In other words, spectral congestion can be eliminated by developing an architecture that would allow spatial multiplexing. The concept of cellular architecture [3, 5, 6, 9] became the turning point in wireless communication technologies based on frequency reuse. The success of spatial multiplexing depends not only on elimination of interferences but also to provide continuous uninterrupted coverage. To provide continuous coverage, the uncovered gaps in coverage area should be serviced by the transceivers operating with frequencies different from the previously deployed transceivers. The proposed deployment of transceivers is equivalent to partitioning of a large coverage area using certain small finite continuous area which may be appropriately called as a cell and serviced by a single transceiver.
© Springer Nature Singapore Pte Ltd. 2017 R.K. Ghosh, Wireless Networking and Mobile Data Management, DOI 10.1007/978-981-10-3941-6_2
21
22
2 Cellular Wireless Communication
The frequency reuse problem can be viewed in terms of map coloring. In a map, regions are typically demarcated by different colors. If two adjacent regions are colored by same color then it is difficult to distinguish one from the other. Since, multi-colored printing is expensive, as few colors as possible should be used for coloring of a map. It is well known that map coloring can be accomplished by use of four colors [11]. In a way, frequency reuse can be seen as similar to reuse of colors in coloring of a map. There are, however, many differences. Frequency reuse requires a minimum separation between cells which is dependent on the strength of signal interferences between the cells
Data Loading...
