1、- = 4855232 0523233 33b 68 Rw. ITU-R M.1032 RECOMMENDATION ITU-R M.1032 TECHNICAL AND OPERATIONAL CHARACTERISTICS OF LAND MOBILE SYSTEMS USING MULTI-CHANNEL ACCESS TECHNIQUES WITHOUT A CENTRAL CONTROLLER (Question ITU-R 71/8) ( 1994) The ITU Radiocommunication Assembly, considering that new land mob
2、ile applications, such as personal radios, providing communications up to a maximum of that these personal radios have characteristics differing from existing services and may be available to a large a) 5 km in urban areas and 15 km in rural areas, are being introduced; b) public; c access technique
3、s conserves frequency spectrum; d) control of the radio path, that the utilization of the radio spectrum should be as economical as possible and that the use of multi-channel that highly flexible and economical systems can be achieved without using a central controller for setting up recommends i. a
4、ppropriate protocols that do not require the use of a central controller for the detection of an idle radio channel; 2. that these personal radio applications should include the use of multi-channel access techniques and that the technology as described below should be used in the development of sys
5、tems: 2.1 Principle of operation The principle of operation of multi-channel techniques without a central controller is as follows: All radios in the system are normally in the standby state on a control channel, ready to receive a selective calling signal. A calling station looks for and finds an i
6、dle traffic channel and stores its number in its memory. Then the calling station transmits on a control channel, a selective calling signal including at least its own identity, the identity of the called station and the number of the identified idle channel. The standby stations detecting their ide
7、ntity code in the received signal, move to the indicated traffic channel and enter into communication. At the end of the communication all units return again to the standby mode. 2.2 Speczjc systems Two systems have been developed according to this principle. System 1 - “Personal Radio System”, base
8、d on analogue modulation techniques and provides voice services in System 2 - “Digital Short Range Radio”, based on digital modulation techniques and provides voice and data services which can be applied both in a one-frequency simplex mode of operation and a two-frequency semi-duplex mode of operat
9、ion. Both systems work in the 900 MHz frequency band. They provide up to 80 channels and use a transmit power a one-frequency simplex mode of operation. of up to 5 W. More detailed data of these systems are given in Annexes 1 and 2. 2.3 Summary The design of systems using multi-channel access techni
10、ques without a central controller allows for economical communication with relatively high reliability. It may combine the advantages of digital modulation for voice and data and the ability to operate in either single or two-frequency mode. Further, the protocols allow both modes of operation with
11、the same frequency allocation to co-exist in the same geographical area. 4855232 0523234 072 Rec. ITU-R M.1032 ANNEX 1 Personal radio system 69 1. Introduction This Annex relates to the personal radio system used in Japan and introduces the basic characteristics, connecting procedure, and receiver i
12、nput level versus connection reliability. 2. 2. z 2.2 2.3 2.4 2.5 2.6 3. 3. z Basic characteristics Frequency: Channel separation: Number of channels: Class of emission: Type of operation: RF power output: Connecting procedure 903.0125 to 904.9875 MHz 25 kHz 80 (one control channel and 79 traffic ch
13、annels) ED: control channel F3E: traffic channels Simplex 5w Configuration of control signal An automatic transmitter identification system (ATIS) is included in a read-only memory (ROM) obtained from the licensing authority. The ROM is required for the operation of the personal radio system (PRS) t
14、ransceivers. Code configuration for A TIS and circuit linkage Bit synchronization: Word synchronization: Selective calling number: Channel number: 8 bits, binary Reserved bits: 4 bits, O000 50 bits, 101010 . 15 bits, 11 101 1001010000 20 bits, 5 BCD bits ATIS code: 48 bits binary: identification cod
15、es (for more than ten million stations, licence issue date and scrambling) Length of Hagelbarger code: Total: 2 x data bit length + 12 = 172 bits 172 + 65 = 237 bits (197.5 ms) Code type: NRZ Bit-rate: 1200 bit/s Modulation method: MSK i 200 Hz, mark 1 800 Hz, space 3.2 Receiver (RX) input versus co
16、nnection reliability In Fig. 1, an example of receiver input level versus bit-error ratio (BER) is shown. Line C of BER = corresponds to 90% connection reliability for the personal radio system. Y855232 0523235 TO9 Rec. ITU-R M.1032 3.3 Flow chart lo- 5 2 1 o-z 5 2 1 5 2 1 o“ 5 2 1 o- FiGRE 1 Receiv
17、er input level versw bit-error ratio performance -10 -5 O 5 10 15 20 Receiver input level (dB(pV) Curves A: Rayleigh fading: - centre frequency: 903.8875 MHz - fading frequency: 20 Hz B: nofadmg C: connection reliability: 90% or more Wf Figure 2 is a simplified communication procedure flow chart for
18、 the personal radio system. The procedure of connection is as follows. All the radios in the system are in the standby state on the control channel. The calling station looks for and finds an idle traffic channel and stores the channel number in its memory. Then it emits the control signal on the co
19、ntrol channel. Those radios whose selective call number coincides with the control signal transfer to the specified traffic channel and enter into conversation. The call sign consisting of the ATIS code is automatically transmitted before the start of conversation, every 60 s during the conversation
20、 and at the end of the conversation. A selective call number is specified before transmission. On the other hand, up to two selective call numbers can be set for receiving. 4855232 052321b 945 = Rec. ITU-R M.1032 71 FIGURE 2 Simplified communication procedure flow chart Radio I O Standby on control
21、Calling 0 on a traffic channel Ihestnld“ Shtc e on control channel control on traaic 0 Transmit Conversation aiimt tiiia(SlliI0i.b AlX3aRiiina (im0)siPts (“Threshold level. Radio 2 - N 3 ntrol 7 Receive G- * (Simplex) ri Conversation The standard threshold carrier level for the receiver is set at 1
22、pV (open voltage). (2)In consideration of trafic congestion, a conversation timer is provided. 485521f2 0523217 881 72 Rec. ITU-R M.1032 ANNEX 2 Digital short range radio 1. Introduction This Annex relates to the Digital Short Range Radio (DSRR) according to an Interim-European Telecommunication Sta
23、ndard developed by the European Telecommunications Standards Institute (ETSI) ETSI, 19931. 2. Basic characteristics 2.1 The DSRR system consists of two control channels and 76 traffic channels with a channel separation of 25 kHz. It is capable of operating in either a single frequency simplex and/or
24、 in a two frequency semi-duplex mode. Direct carrier modulation is used to send the selective signalling codes and voice or data messages. Three principie elements are specified: units, master units and repeaters. 2.2 2.3 2.4 2.5 2.6 2.7 2.8 2.9 Frequencies: simplex: semi-duplex: paired with: Channe
25、l separation: Number of channels: Channel allocation: Type of modulation: Modulation rate: RF power output: Transmitter adjacent channel power: 3. Signalling 933.0375-934.9625 MHz 888.0375-889.9625 MHz (unit transmit) 933.0375-934.9625 MHz (master unit and repeater transmit) 25 kHz 78 control channe
26、ls 26 and 52 traffic channels O1 to 25,27 to 51, 53 to 78 GMSK 16 kbit/s (speech and data) (BT value of 0.3) 4 kbiih (signalling) (BT value of 0.5) 4 W maximum less than -70 dBc outside the 2 MHz sub-band less than -50 dBc inside the 2 MHz sub-band 3.1 synchronization and codeword repeated three tim
27、es. The selective signalling code (SSC) consists of a bit synchronizing preamble followed by the frame 4855232 U523238 718 M Rec. ITU-R M.1032 Bit sync (preamble) Frame sync Code w ord SSC number Traffic channel code First call code (unit to which the SSC is sent) Command code Reserved Codeword coun
28、ter Manufacturers code Second call code (the transmitting unit) Cyclic redundancy check (CRC) Sub total 104 bits x3 312 bits 73 256 bits i6 bits i bit 7 bits 24 bits 4 bits 2 bits 2 bits 8 bits 24 bits 16 bits Total 568 bits 4. Source coding 4.1 Voice transmissions The speech coding algorithm for tr
29、ansmission and reception is in accordance with the standard adopted within the GSM Digital Pan-European Cellular Radio specification. The specification for transcoder delay is relaxed to a figure of less than 100 ms. The channel coding protects the 34 most important bits in the 260 bit speech frame
30、by use of convolution coding, parity, tail-biting and interleaving techniques. 4.2 Data transmissions The coding system used for data transmission and reception is left to the manufacturers discretion. 5. Operating procedure 5.1 Singlefrequency working (see Fig. 3) All radios in the system are norma
31、lly in the standby state, that is ready to receive a SSC on one of the two control channels. (Units with even number serial numbers normally listen on their primary control channel 26 and odd serial numbers on channel 52.) A calling unit first scans and finds a free traffic channel, then communicate
32、s via the relevant control channel using the selective signalling code to alert an individual unit or group of units. These units transfer to the traffic channel and enter into conversation. At the end of the conversation ail units return to the standby state. 5.2 Twofrequency working (see Fig. 4) A
33、 similar strategy to that described in 9 5.1 is adopted with the exception that the protocol is modified such that the master unit or repeater always scans for a free traffic channel irrespective of the origin of the call. Should a two frequency unit initiate a call the first SSC contains no traffic
34、 channel number (set to all zeros) and the master unit or repeater has the responsibility of making the allocation. This is because in most systems of this type the master station or repeater will have a better antenna position giving greater coverage. 74 Calling unit Called unit TX 4855232 0523239
35、654 Rec. ITU-R M.1032 FIGURE 3 Single frequency individual call set-up (no re-tries) Communication mode (maximum 3 min) CC procedure TC procedure - I I I 200 200 200 200 200 200 10 s 5s (mis default) min min max rnax max max RF: Free: 4 kbit/s: SSC ACK 16 kbius: observing the RF level on the traffic
36、 channel monitoring the control channel to determine whether it is free or not receiving with the signalling modulation scheme (waiting far an SSC or an ACK) transmitting an SSC (142 ms) transmitting an ACK (142 ms) transmitting or receiving with the voicddata modulation scheme :b Tx Al Fa Tx Rx Tx
37、.1, CC procedure m 4855232 0523220 376 Rec. ITU-R M.1032 Communtauon TC procedure 75 FIGURE 4 Two frequency cai1 Set-up unit to unit through a repeater (no re-tries) I l I I I ll 1 I I l (mis 200 200 200 default) Min Min Free: RF: 4 kbit/s: ssc: ACK: ID: 16 kbit/s: 200 ux) 200 58 200 400 400 400 400
38、 10 s Min MaxMin Max Max Max Max A: R: B: callingunit (on Bs primary CC) repeater (on Bs primary CC) called unit (on Bs primary CC) monitoring the control channel to determine whether it is free or not repeater observing the RF level on the traffic channel receiving with the signalling modulation sc
39、heme (waiting for an SSC or an ACK) transmitting an SSC (142 ms) transmitting an ACK (142 ms) repeater transmitting its identification SSC (142 ms) transmitting or receiving with the voicddata modulation scheme REFERENCES ETSI 19931 LETS 300- 168, Digital Short Range Radio. European Telecommunications Standards Institute, Sophia Antipolis, F-06921, Valbonne Cedex, France.
