1. Basic requirements of wireless systems provision

Basic parametric information about communication systems, wich are usefull for effective wireless system designing are presentred on the Table 1.1.

Table 1.1. Basic parametric information about wireless communication systems.

Basic requirements to the received messages	Existent limited resources of the wireless system	Loses in the communication channel	Additional requirements to the received messages
1	2	3	4
Transfer rate, R	Bandwith (В) at the set spectrum range	Distance loses, АD	Communication loses, D
Bit error rate, Pb	The transmitter power, Рt	Loses on the passive hindrances, АP
Signal to noise ratio, Eb/No		Loses on the actіve hindrances, АА

This chapter considers basic information about provision of requirements of messages considering resoureces limitation and system loses.

1. The brief analyisis of the main requirements of wireless communication systems.

Basic reqirements of wireless communication systems are related with provivsion on the output of receiver an informational signal with following parameters:

P_b ≤ P_{bnom .} (1.1, a )

R ≥ R _nom, bit/s (1.1, b)

where P_b , P_bnom - bit error rate (BER) and its nominal value, consequently; R, R_nom.- transfer rate and its nominal value, consequently.

Thus, system should provide technical requirements, that shown on Fig. 1.1.

a) b) c)

Fig. 1.1. Basic requirements of wireless communication systems: (a) – by transfer rate R; (b) – by bit error rate P_b; (c) - by R and P_b simultaneously.

The logical question: what should be the reserve values R and P_b relatively to their nominal values? On the very first view we could conclude that is better to have more reserve value, and even under influence of different destabilizing factors the system will be operating properly. But, from different point of view such system is more expensive on the stage of installation, so on the stage of exploitation. Consequently, this work analyzes communicational system in the area close to conditions (1.1, a ,b) with a small reserve – about 10-20%.

The basic dependencies underlying implementation of these conditions (1.1 a, b​​) are as follows:

• the value P_b is determining through Gaussian error integral::

(1.2, a)

• the value R is determining by Shannon-Hartley theorem:

C=Blog₂(1+S/N) (1.2, b)

where С=R_max – is the throughtput capacity of the communication system, which determines maximal transfer rate R; S/N - signal to noise ratio.

It should be noted that integral (1.2, a) couldn’t be calculated by straightforward integration, but numerical, that may complicate the analysis of wireless communication systems.

However to provide set technical requirements system should be provided with some resources, as is clear from (1.2, b).