47.7.3 Personal communications

The term PCN, Personal Communications Network, is used widely in the UK, whilst PCS, Personal Communications Services is used in the USA. Both aim at the same objective of serving the mass consumer market with mobile communications. The key challenge is to provide a very high capacity network to support a large number of users at low cost. Microcellular techniques will certainly be needed, and in order to keep costs down, the concept of regional service, and local access to the PSTN is being considered. IN techniques may offer personal numbering across a variety of net­works.

PCN is dealt with in detail in Chapter 48. The standard in Europe, known as DCS1800 is based on the GSM standard but operating at 1800MHz. There is therefore unlikely to be a significant technical difference between Cellular GSM and PCN, with microcellular techniques being equally applicable to either system.

In the USA, the use of CDMA, code division multiple access, is being trialled for PCS. CDMA works on the principle of transmit­ting unique (orthogonal) codes to identify different users. Detection of signals is achieved by using correlating receivers such that other users appear as pseudonoise. CDMA thus allows a large number of users to share the same (wideband) radio channel.

There is considerable debate about the advantages and disadvant­ages of CDMA, in particular how to control near/far user inter­ference; the extent to which this can be achieved is crucial to the ultimate capacity of CDMA. One of the key benefits of CDMA is the potential to share spectrum with other users, for example fixed links, and for this reason it is particularly attractive where additional spectrum for mobile systems cannot be made available.

47.8 Conclusion

Cellular radio is a comparatively young technology. Networks em­ploying analogue systems have developed rapidly and now provide high quality service and excellent coverage in many of the de­veloped countries. Technology developments are now increasing the potential network capacity, reducing the size of mobiles, and bringing advanced features and services to the mobile user. The decade ahead with the opportunity to introduce new digital systems and create a world-wide land mobile standard looks particularly exciting.

Exercise 1 Write out of the text (47.6 – 47.8) all terms referring to cellular

radio systems. Give their Russian equivalents

Exercise 2 Words to remember:

HDLC protocol- (High Level-Data-Link Control)	высокоуровневое управление каналом (передачей) данных
forward error correction	прямое исправление ошибок
contiguous coverage	соприкасающиеся зоны обслуживания
CDMQ –(code division multiple access)	коллективный (многостанционный) доступ с кодовым разделением каналов
ultimate capacity	придельная способность
noise performance	шумовая характеристика
relevance	соответствие, отношение
to divert	отклонять, отводить, изменять маршрут
infomation service = enquery office	телефонная справочная служба

Exercise 3 Read the text and translate it without a dictionary

Exercise 4 Speak on the problems (work in pairs):

1	supplementary services (the most typical ones)
2	value added services
3	data services

Exercise 5 Answer the following questions:

1	What is the primary purpose of all cellular radio networks?
2	Do they offer a range of supplementary and value added services?
3	What are the typical supplementary cervices?
4	Which of value added services are considered to be the most important?
5	Can you ask your groupmates 4-6 questions about data services? (47.6.3 Data Services)?
6	How can you prove that the technology of cellular radio systems continues to develop very rapidly?
7	What do microcellular techniques allow to achieve?
8	What are these developments aimed at?
9	One way of easing handover problems is to employ an “umbrella cell”, isn’t it?
10	What advanced services do intelligent networks provide?
11	Is there any difference between the term PCN and the term PCS?
12	What are the main advantages of CDMA?