A radio based communication system for an indoor network requires to deal with the problems that are caused by a large number of communicating devices operating at the same, and at similar operating frequencies. Where two devices are transmitting on the same frequency, the receiver experiences co-channel interference if both of the transmitters are within a certain range of the receiver. The interference caused here can be controlled by restricting the separation of the two transmitters to be greater than some defined reuse distance or using some means of dividing the transmission time between the two transmitters so that only one is operational at any one time. In the case of two transmitters operating within adjacent frequency bands, adjacent channel interference may occur. This can be minimised by judicious design of the modulation scheme.
One possible connection scheme involves dividing up a building into a number of local radio communication sites, or cells. Typically each cell is assigned a set of frequencies that differ from all adjacent cells. These frequencies may be reused in another cell that is separated from the first by at least the reuse distance. These cells could be connected either by a point to point radio link, or by high capacity wire based connections. As the number of cell sites is significantly smaller than the number of communicating devices, the additional cost of forming the backbone connection out of a wire based technology is not unreasonable. Different types of communications will have different requirements of the network, each requiring specialised functions. For voice based communications, redundancy can be exploited, and accurate information transferral is not essential. For data communications, the communication can be slow, but must be accurate. In a multiple base system using a packet based system where computer communications take place using a set of communication blocks, it is possible for the packets of communication to arrive at the receiver out of sequence. This situation can be dealt with using communication protocols to reconstruct the transmitted signal.
One possible connection scheme involves dividing up a building into a number of local radio communication sites, or cells. Typically each cell is assigned a set of frequencies that differ from all adjacent cells. These frequencies may be reused in another cell that is separated from the first by at least the reuse distance. These cells could be connected either by a point to point radio link, or by high capacity wire based connections. As the number of cell sites is significantly smaller than the number of communicating devices, the additional cost of forming the backbone connection out of a wire based technology is not unreasonable. Different types of communications will have different requirements of the network, each requiring specialised functions. For voice based communications, redundancy can be exploited, and accurate information transferral is not essential. For data communications, the communication can be slow, but must be accurate. In a multiple base system using a packet based system where computer communications take place using a set of communication blocks, it is possible for the packets of communication to arrive at the receiver out of sequence. This situation can be dealt with using communication protocols to reconstruct the transmitted signal.
Posts
No comments:
Post a Comment