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1-1HISTORY REVIEW Paging is a one - way broadcast signaling system. It can send data only, data and voice messages, numeric displays, Alphanumeric and/or message alphanumeric paging system displays . became

available in the mid - 1980 s [6 ]. Paging is a mobile communication service without two -way speech

Facilities. Paging systems are designed as extensions of the telephone network. The first land mobile radio system, the one - way information broadcast concept was pioneered by the Detroit Police Depart ment in Michigan ,in the USA in 1921 [l ]. Local radio paging has been offered in the USA since about 1950 [6 ]. The term paging, in general, refers to sending short messages to some one in the move with some defined coverage (e.g. a building, compus, city, country, or region). The paging system is a simple application of mobile radio systems, where we send the signal from the transmitter without assurance that the message has actually, arrived at (or acknowledged by) the

intended receiver Paging is a ''one - way'' system.

This project will study the paging system as a mobile data system, discuss system structure, and review coding techniques as employed in paging systems. in addition, paging standards will be reviewed and compared. Finally the existing pu blic paging systems in Saudi Arabia will be studied.

2.1 INTRODUCTION The paging system consists of: The caller network, and Paging service . The caller network connects into the paging service via the normal local telephone exchange (Publ ic Switched Telephone Network (PSTN ) or Mobile Network (MN) etc . . . )

The paging system components include : Paging control units, Area controllers, Modems, and

Transmitters (TX). Each paging terminal receiver in this system is uniquely identified by an address code. For example, when a caller needs to send a message through this system to a subscriber, he will use the telephone terminal and enter the code number

(paging number ) of the subscriber, this message is routed by the switched telephone network to a central server of the paging network, and is then transmitted on a radio channel into a given region. The advantages of paging over other radio

communication services lies in the simplicity of its concept; messages are sent via a radio channel to a receiving terminal situated within a given area. The receiver is very simple. This reflects on cheaper cost of paging services and terminals compared to other more powerful communication services . Paging has limited capabilities allowing only one w a y store and-forward data transmission. This is in contrast to the different services of public telephone networks and mobile communication networks .

This chapter will include description of the basic parts of paging system, the classes of paging systems, t he system capacity, frequency bands,

signaling formats (coding), and receiver . 2.2 BASIC PARTS OF PAGING SYSTEM The basic parts of paging system are: . Access / Voice Messaging Units 'Caller Network' . . Paging Terminal . Transmission Network. . Transmitter Equipment . ''The last three can be called Paging Service''

2.2.1 ACCESS / VOICE MESSAGING UNITS . This unit is used to connect the caller to the paging terminal. This procedure can be done by normal local telephone exchange (public switched telephone

network (PSTN ) or mobile network etc.) or via PSPDN ( e.g. X. 25 Alwaseet ) using modems, or via telex. For access method different kinds of access units are needed. These are : *Tele Access Unit (TAU ) for direct telephone access .

*Data Access Unit (DAU ) for operator assisted access . *Telex Access Unit (XAU ) for telex access. * Serial port and modems for X.25 access . 2.2.2 PAGING TERMINAL The paging terminal consists of two units: a) Paging Network Controller (PNC ) : Paging Network Controller (PNC) communicates

with the access devices (e.g. TAU,DAU, etc.), stores, and handles customer messages. The PNC - OMC inter working is managed by PNC. b) Operation and Maintenance Center (OMC). The paging system operation and maintenance

functions are concentrated on the OMC. This means all network management, administration and

maintenance functions. The OMC provides traffic and quality of service statistics . From the OMC we can load to all network elements new software without physically visiting the

different sites. 2.2.3 TRANSMISSION NETWORK.

The transmission network consists of : a) Paging Area Controller (PAC ). The PAC receives paging messages from the Paging Network Controller (PNC ), buffers them in queues, and sends these messages to Base Stations (B S) for transmission. The PAC performs error correcting coding to protect against errors in the Transmission Network.

b) Network Router (NR). Network Routers (NR) act as communication nodes providing PAC co nnection to a number of Base stations (B S). The use of Network Routers (NRs) minimizes the line cost by linking the same

information to many outputs. The Network Router (NR) can acts as multiplexer/ demultiplexer . One of the Network Router (NR)

functions is message routing, which routing messages from PAC to the correct NR or NR's and to the BS or BS's. 2.2.4 TRANSMITTER EQUIPMENT The transmitter equipment used consists of : a) Base Station Controller (BSC ):

The functions of BSC are : handling traffic pa ges, time management and Synchronization, and

controlling the operation of the Transmitter and antenna system. b) Transmitters (TX) c) Antenna System. 2.3 CLASSES OF PAGING SYSTEMS . There are two main classes of paging systems : on site paging systems and wide area paging systems . 2.3.1 ON - SITE PAGING SYSTEMS . As this name indicates the on - site paging system is a private system or a closed system which covers a specified area (e.g. a hospital, a company, an airport, a factory, an office etc . ). This means that it is for internal use and for short distances . A small modem paging system will

probably consist of a transcoder and few tone or numeric pagers. The transcoder is a combined digital paging encoder consisting of a keyboard and a 10 digit display, and a small 1W transmitter

incorporating an integral microphone . Large on ­ site

systems may have a remotely linked section of the system as would be found in a multi - sited hospital complex. Such large system may have up to 1500 pagers. For a small system 0.5 W at UHF and 1 W at HF are sufficient transmitter RF powers to satisfy the small site applications, and these can be integrated with the encoder . For a large system, high powers are required : in general 5 w ERP in Europe . [3 ] 2.3.2 WIDE AREA PAGING SYSTEM Wide area paging system offer paging services to the public in a city or a country. City wide paging was developed by Bell labs in the USA in the early 1960s, followed by the Dutch PTT. Then in 1978 the UK British Post Office announced digi tal paging system, POCSAG (Post Office Code Standardization Advisory Group). This became the CCIR Radio Paging Code (RPC) No. 1 and was adopted as standard [3 ]. In this system, the covered area is divided into zones with transmitters of typically 100 W/250 W to cover

the zones. Now wide area paging systems have different standards including POCSAG, ERMES, and FLEX (developed by Motorola).

2.4 SYSTEM CAPACITY . Paging systems capacity can be divided in four different kinds, as follows : 1 ) Air-time capacity ''output capacity''. 2) Access capacity ''input capacity'' . 3) Processing capacity ''for paging and voice

messaging'' . 4) Database capacity ''for paging and voice

messaging'' . The capacity of any paging system is effected by the following [4 ]: * Number and characteristics of the radio channels used. * The number of times each channel is re-used within the system. * The actual paging location requirements of the individual users.

* The peak information (address and message) requirements in a location or locations. *Tolerable paging delay. *Data transmission rate. *Code efficiency. *Method of using the total code capacity throughout the system. *Any inefficiencies introduced by battery - saving provisions . *Possible telephone system input restrictio ns. 2.5 FREQUENCY BANDS Allocated frequency bands for paging systems vary from country to country. The ITU specify the

following frequency bands for mobile services [4] : 164- 174 MHz 68 ­ 88 MHz 806 - 960 MHz 26.l ­ 50 MHz. 450 - 470 MHz.

In the USA and Canada ,for example, to cover both countries pager manufactures have to provide for 27 MHz - 50 MHz HF; 138 MHz - 174 MHz VHF ; 445 MHz - 470 MHz UHF ; 900 MHz is also popular in these countries. 931 MHz is used for satellite paging [3]. Another example, in

the UK for on - site we have 26 .2375 to 26.8655 MHz and for wide area ''VHF 169.425 to 169.80 MHz, UHF 454.0125 to 454 .825 MHz,'' for ERMES standard. In Saudi Arabia the POCSAG paging system uses the operation frequency of 147.65 MHz and for E RMES paging system the operating

frequency 169.4 MHz to 169.8 MHz on the VHF band. To choose a suitable radio - frequency band we must consider the following factors [4] : * Economics of the system for a given area. * Availability of frequencies . * Propagation considerations and operational requirements . * Receiver sensitivity. *Permitted limits of emitted power levels and

antenna heights according to local regulations. * Levels of paging traffic. * Environmental noise level .

2.6 SIGNALING FORMATS / CODING

The code and format provides queuing and numeric / alphanumeric message flexibility and ability to

operate in a mixed ­ mode transmission with other formats. The Electronic Industries Association (EIA) US has established in the

100 standard two - and five -

sequential - tone codes in the 67 .0 - to 1687 .2 Hz frequency range [3]. Pager manufactures have added additional proprietary tone codes extending the

frequency range, the number of tones, and the number of pages which can be called. The two - and five sequential tone codes are replaced now by digital selective calling systems. Error Correcting Codes used in paging systems usually are cyclic codes. For example ERMES paging system uses the shortened cyclic code (30,l8) as its error correcting co de, and the POCSAG paging system uses the BCH (32,21 ) as its error correcting code.

The ERMES system information is 36 bits in length [5]: 13 bits are being used to identify the networks .

6 bits to identify the paging area (this number of bits will allow up to 64 areas to be paged). 5 bits for the receiver to decide which channel it should look to in order to receive a call . 11 bits for batch sub - sequencing and numbers, and one bit is a spare bit for future use. 2.7 RECEIVERS . There are many models of pager receivers . They differ in size; the large model can display up to 1000 characters in 16 ­ character blocks on an LCD screen. The important property of pager receiver

design is to achieve high operating sensitivity. A 3 dB carrier to - noise rat io produces a signaling response in most modern paging receivers [2 ] . We can classify the paging receivers in three types. A tone receiver has a number of audible tone patterns to alert, but it does not display numbers or messages (old and simple type). The numeric pager has a display of typically 12 or 24 digits, that enables the caller to send a telephone number . The third type is

the alphanumeric pagers, which has a display of 16, 32, or 80 characters [3 ]. For each standard of paging there are special specifications for each Pager receiver.

3.1 INTRODUCTION We can divide the paging system into two classes :Class ­ 1: Is the old paging systems that operate at low speeds and have low capacity. Examples of these systems include POCSAG

standard (1978) and Swedish Mobilosoeking systems (MBS) (l978 ) [3]. Class ­ 2:

Is the new paging systems that operate at high speeds and have large capacity. These systems include the ERMES system (1992 ) and FLEX system (l993). 3.2 POCSAG The Post Offi ce Code Standardization Advisory

Group (POCSAG ) standard was drawn in 1978 by the British Post Office. In 1980 the POCSAG was adopted by the CCIR as Radio Paging Code No .1 (RPC 1 ). The POCSAG specifications are listed in Table 3 . 1 [3]. Parameter Transmitter frequency Channel spacing 20 or 25 KHz (depending on country). Transmission rate Data rate Modulation Error Correction 1200±10Baud 512 or 1200 bit/ sec NRZ FSK ±4.5 KHz 2 bits; BCH(32,2 l ) Value 146 MHz to 174 MHz

Deviation ±4.0 or 4 .5 KHz (depending on

country) Signal rise time Table 3.1 POCSAG Specification The POCSAG standard is well established in the GCC countries as a first paging standard. For example, Saudi Arabia has 193 ,000 subscribers, Kuwait 150.000 , Bahrain 61 ,000 , Qatar 46,000 . The UAE 217.214 and Oman has 51,546 subscribers [7]. The POCSAG at 1200 bit/sec can be upgraded to get POCSAG at 2400 bit/ sec. The upgraded system has twice the existing capacity and could require 10% more transmitters to give equal coverage area . The POCSAG system services are: Tone - only paging, Numeric paging, and Alphanumeric paging. 3.3 ERMES ''European Radio Message System'' ERMES. This system started in December 1992 [3]. This standard was designed by a team of international expert s operators from paging manufactures with and the Institute network European (ETSI). < 275 µs.

that

worked

Telecommunications

Standards

ERMES is the only open-system, high-speed paging standard to be recommended by the International

Telecommunications Union (ITU) [7 ], and it is the only standard which has been designed from the outset to permit roaming over long distances, within the "mother " Country and externally to other

Countries. ERMES was developed mainly for alphanumeric messages . If it is used for numeric messages the efficiency drops to little better than POCSAG

running time at 2400 bit/sec [8]. The world's first ERMES International roaming agreement was signed by the Swiss and French PTTs at the Telecom 95 show in Geneva . The Tecnomen Company gave the firs t public demonstration of world wide ERMES roaming. The company

transmitted messages from Saudi Arabia, via the Swiss PTT's ERMES system, that were picked up by NEC pagers roaming from Saudi Arabia to

Switzerland [8]. The ERMES specifications are listed i n Table 3.2 [3]. The ERMES system provides national and

international paging services. The ERMES system services are: Tone-only paging, Numeric paging Alphanumeric paging, and Transparent data paging.

Parameters . Frequency range

Value 169.4125 MHz to 169.8125 MHz

Channels

16 Channels, 25 KHz spacing

Modulation

4 level (4-PAM/F M) ±4687.5 Hz and ±1562.5 Hz

Data rate Symbol rate Error correction

6.25 kbit / sec 3.125 k baud 2 bits, (30,18 ) shortened cyclic code

Interleaving to provide Message only to a depth of burst error Correction Table 3.2 Specifications of ERMES. 3.4 FLEX 9 code words.

FLEX is a result of working in Motorola Paging Products Group. Motorola is aggressively marketing FLEX as a world paging standard. FLEX was introduced in June 1993 in response to increased pager mobility, increased demand for low cost delivering of long messages, and more frequent communications. FLEX can handle over 600 ,000 pagers per channel and the protocol supports over a billion addresses. FLEX is a high speed paging protocol running at three different speeds 1600, 3200 and 6400 bit/sec, the fade protection is 10 m sec at all speeds and two bit error correction. FLEX is being used in the USA, Japan and China [8].

4.1 INTRODUCTION

Saudi Arabia is among the first countries in the Middle East that started public paging services. Saudi PTT planned the paging network to initially cover the major cities like Riyadh, Jeddah, and Dammam. It then developed this network to cover other large towns - in the Kingdom of Saudi Arabia. Firstly, in 1412- 1413 A.H. (1992 ) Saudi PTT adopted the POCSAG standard as the Public Radio Paging System (PRPS) to operate in its region. This network operated in 16 cities . After initial service offering and the result ing high demand, Saudi PTT decided to increase the paging network capacity by high speed and large capacity new paging standard. The ERMES standard was selected in the second part of the paging system project in the country . This chapter will include a study of POCSAG system as well as the ERMES system used in Kingdom of Saudi Arabia, and will give description of these systems. 4.2 THE POCSAG NETWORK. 4.2.1 INTRODUCTION

The

Ministry

of

PTT

introduced

the

POCSAG

standard as Public Radio Paging service in the Kingdom of Saudi Arabia in 1992 . POCSAG service coverage includes sixteen (16) major cities. 4.2.2 SYSTEM DESCRPTION POCSAG, Public Radio Paging System (PRPS) have three Central Paging Control Terminals (CPCT) located in Riyadh to service the Central Region, in Jeddah to service the Western and the Southern Regions, and in Dammam to service the Eastern Region. These CPCT's are interfaced with the Public

Switched Telephone Network (PSTN) via R2 trunk spans. Riyadh and Jeddah have seven R2 trunk spans each, and Dammam has five 9 trunk spans. In each of these sites there are a number of Radio Paging Transmitters (RPT's). The number of these RPT's varies from one site to another according on the coverage area requirements. For example, in Riyadh City there are seven RPT's , whereas AlKharj has only one RPT. The three CPCT's are connected together through Fixed 9 .6 kbps dedicated line data links to carry messages from one CPCT to

another, when some subscribers need to receive their paging messages as they roam outside their home coverage area (national roaming). The CPCT are also interfaced. to the Radio Paging Transmitters (RPT' s) in various locations. The POCSAG system operates with both POCSAG rate (512 bps) and SUPER POCSAG rate (1200 bps), with service of tone - only or numeric pagers. The RPT's operates at frequency of 147.650 MHz. 4.2.3 NETWORK COMPONENTS . The POCSAG network consists of: 1 ) Central Paging Control Terminal (CPCT) The CPCT is connected to the Public Switched Telephone Network (PSTN ), and the other network components . 2) Digital System Control Unit (DSC ). 3) Radio Paging Transmitter (R P T). 4) surveillance. 4.2.4 COVERAGE AREA

The Coverage area of POCSAG system include these cities: 3.Buraydh 6.Abqaiq 9.Hail 12.Madinah 15.Tabuk 2.Al-Kharj 5.Dammam 8.Jubail 11.Makkah 14.Baha 1.Riyadh 4.Unayzah 7.Hofuf 10.jeddah 13.Taif 16.Yanbu .

4.3 THE ERMES NETWORK 4.3.1 INTRODUCTION The Ministry of PTT introduced ERMES paging system as the second part of the paging services in the Kingdom of Saudi Arabia. ERMES system coverage areas include the same area coveraged by the POCSAG system (i.e. the sixteen cities) and additional cities. This service started at the first of SHABAN 1416 A.H. (23th December 1995).

4.3.2 SYSTEM DESCRIPTION. The ERMES system has three Paging Network

Controllers (PNCs). These PNCs are located in Riyadh to service the Central Region, Jeddah to service the Western and Southern Regions, and Dammam to service the Eastern and the. North Eastern Regions . These PNCs are connected to each other over separate 19.2 k bps X.25 links to provide national roaming. This system is initially designed to provide service to 720,000 subscribers . The system can be upgraded to one million subscribers, wit h 75% of this service as numeric, 25% alphanumeric and 26.67% of the numeric subscribers are considered as voice mail subscribers. Currently only numeric service is

offered. Alphanumeric and voice mail services are planned for the next phase. 4.3.3 NETWORK CONFIGURATION The ERMES paging system can be configured in several ways . The ERMES paging system consists of :

1. Paging Network Controller (PNC). 2. Paging Area Controller (PAC ). 3. Paging Area Controller - Network (PAC -NR). 4. Tele Access Units (T AU). 5. Data Access Units (DAU). 6. Operation and Maintenance Center (OMC). 7. Network Router (NR) 8. Base Stations (B S). Fig. 4.1 Illustrates the block diagram of the ERMES paging system and Fig. 4 .2 illustrates the ERMES system block diagram for the Central Region. 4.3.4 COVERAGE AREAS The ERMES paging system covers the following cities :For the Central Region 2.Al-Kharj 4.Hutymala 6.Majma 8.Hotat B.Tamimi 10.Zulfi 12. Unayzah 14.Bukariya 1.Riyadh 3.Muzahmia 5.Sulayil 7.Hotat Sudayr 9.Midnab 11. Buriayadah 13.Al-Ras 15. Hail

For the Western and Southern Regions :2.Makkah 4.Tabuk 6.Yanbu 1.Jeddah 3.Madina 5.Al-Wajh

8.Abha 10.F.Najran 12.Sharoora 14.Jizan

7.Taif 9.Bisha 11.Kamis mushyt 13.Nimas

For the Eastern and Northern Regions: 2.Al-Khobar 4.Rastanura 6.Jubail 8. H. Batin 10.Rafha 12.Sakaka 1.Dammam 3.Abqaiq 4.Hofuf 7. Al -Khafji 9.KKMC 11.Arar 13. Qurayat

Riyadh City Coverage is implemented using eleven base statio ns located at : 2.Misfah 4.Mursalat 6.Nadheem 8.Shaffa 10.Al-Khazan 1.Maather 3.Naseem 5.Eraijah 7.KhuraisRoad 9.Diriyah 11.KKIA 4.3.5 SUBSCRIBER VOLUME AND TRAFFIC ANALYSIS

The ERMES paging system planed to have 720,000 subscribers .

Riyadh Traffic in Erlang Number of Calls Congestion % . Circuit Blocked MHT (sec) 105.2 26818 1.05% 9.42 14.3 0.17

Jeddah 105.3 23245 0% 10 16 0.12

Dammam 40.9 9223 0% 1 16 0.1

BH calls/ page

Table 4 .2(b) Traffic Analysis * These numbers are taken on average in the busy hours *Mean Holding time (MHT). 4.3.6 SYSTEM PERFORMANCE *Central Region Average message length per page 7.8 characters Total busy hours calls during 8.00 PM to 9.00 P M * Western Region Average message length per page 8.9 characters.

Total busy hours calls during 7.00 PM to 11.00 For Jeddah PM 7.00PM to 8.00 PM For Maddinah and Taif and 11.00 PM to 12.00 P M

Summary : This project the discussed error the paging system; it

discussed

correcting

codes

(ECC ),

especially the block codes which used in paging systems. Then the project study the paging standards, and then paging systems in Saudi Arabia were discussed.

Conclusions: 1.Saudi Arabia will have largest ERMES Public Paging Network when the current Project is

completed. 2. Saudi Arabia PTT had made a good choice, when it adopted t he ERMES system, because it is a world standard, has large capacity, allows international roaming plus many other benefits. 3.Cyclic code s are widely used in pages, because they are easy to generate and decode by using shift registers . 4. During the weekends the number of page calls increased after 9.00 PM, where as in working days they increased after 6.00 P M. This is agreement with the life style and working habits of the Saudi society. 5.We have the same busy hours for working days and weekend days . 6.In Jeddah Region we have long busy hours (From 7.00 PM to 12 .00 P M), whereas in Riyadh and Dammam (From 6.00 PM to 9 .00 P M). This is

accounted for by the difference in life style in the Hijaz area . 7.In the holy month of Ramadan the busy hour shined in all cities, (Riyadh 9.00 to 10 .00 PM, Jeddah 10.00 to 11.00 PM and Dammam 9.00 to 10.00 P M) as

compared with an ordinary month of Shawal. This reflects the ,hanging life style during Ramadan. 8.We have a smaller number of pages in a Ramadan day than a typical day throughout the year. Again this is accounted for by the changing Saudi behavior in Ramadan.

REFERNCES 1) Daniel Minoli, Te lecommunication Technology Handbook, Artech House, 1991 . 2)Donald Finle and Donald christianse, Electronics Engineers Hand Book, Mc Graw-Hill, 1989. 3) Fraidoon Mazdu, Telecommunication Engineers Reference Book, BuHeworth-Heinenmone, 1993 .

4) FREEMAN, Reference manual for communication engineering, John Wiley & sons, lnc., 1994. 5) MIDDLE EAST COWICATIONS, volume 6 No. 4 June 1991 . 6) B.P.Lathi, Modern Digital and Analog

Communication Systems, New, York: Holt, Rinechart & Winston lnc., 1989 . 7) MIDDLE EAST Mobile, March 1996 , Vol. 4 No .2 8) Comm's MEA, Vol . 6 No. 11 , November, 1996

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