Detail radio aspects

Date: 2015-10-07; view: 419.

Part IV (49.4.4 – 49.4.8)

The above applications place a number of requirements on the basic design of the radio system. The following are indicative of this process:

1. Ability to handover between channels on the same base station and between channels on different base stations without dis­turbance to speech or data.

2. Ability to offer variable bit rate channels to data and ISDN options.

3. Ability to cater for the traffic requirements of high capacity business communications systems.

The result of putting all these requirements into practice, includ­ing those of Section 49.2, produced an FDMA/TDMA/TDD system having ten carriers each conveying 12 time division duplex 32kbit/s channels, (see Figures 49. 10 and 49. 11. To achieve the variable bit rate capability DECT is able to concatenate individual 32kbit/s timeslots to build up larger capacities. These concatenated timeslots need not be adjacent or on the same carrier frequency. Potentially the maximum throughput is, therefore, 12 x 32 = 384kbit/s bothway. Handover is another key specified feature of DECT and has been designed to support handovers in 10ms to 15ms.

Other radio parameters are given in Table 49. 2.

Each frame consists of 5ms alternate periods of transmission and reception und it is a general requirement that all base and portable terminals shall be able to operate on all timeslots.

This technical specification indicates that in cluttered, multi-path, environments outside buildings time dispersion may be a problem.

Antenna diversity located at the base station is considered the first line of defence in such instances.