1、232b4L4 000bOL9 b TIL 04-04 E Page 1 Recommendation T/L 04-04 (Edinburgh 1988) HARMONISATION OF 140 MBIT/S DIGITAL, RADIO RELAY SYSTEMS FOR OPERATION BELOW 10 GHz UTILISING 64 QAM AT ABOUT 30 MHz SPACING Recommendation proposed by Working Group T/WG 12 “Transmission and multiplexing” (TM) Text of Re
2、commendation adopted by the “Telecommunications” Commission: 1. INTRODUCTION This Recommendation specifies harmonised parameters for digital radio-relay systems with a channel capacity of 140 Mbitls designed to operate in defined bands below 10 GHz utilising approximately 30 MHz spacing between cros
3、spolar channels. Systems using 64 QAM modulation are considered to fulfill this requirement. Parameters specified fall into two categories: (a) Those that are required to provide compatibility between channels from different sources of equipment on the same route, connected either to separate antenn
4、as or to separate polarisations of the same antenna. This category also includes parameters providing compatibility with the existing radio-relay network. (b) Parameters defining the transmission quality of the proposed systems. The task of defining compatibility requirements with analogue systems o
5、n the same hop is made complex by the fact that analogue systems are not harmonised. Compatibility requirements are therefore limited to allowing operation of digital and analogue channels on separate ports of the same antenna. The harmonisation has been limited to specifying IF and RF characteristi
6、cs, limited baseband parameters, space diversity system specification, and antenna/feeder system requirements. All parameters specified apply over the full range of environmental conditions specified for the equipment (see Recommendation T/TR 02-03). System designs which comply with this Recommendat
7、ion may make use of Forward Error Correction (FEC) or Soft Decision Techniques (SDT) as a means to improve the bit error ratio characteristics. It is not intended that this Recommendation should standardise on any particular type of FEC or SDT realisation. It is considered important, however, that f
8、acilities are provided to verify the performance excluding the advantage of FEC or SDT in order that these techniques do not conceal any aspects of the radio system design which may have degradations with respect to nominal performance, or any external iduences that may be present when the system is
9、 installed in an operational environment (e. g. intermodula- tion products in the antenna system, radar interferences etc.). Unless otherwise specified, BERS given in this Recommendation apply in the case where error correction facilities andtor soft decision techniques are enabled. 2. APPLICATIONS
10、The systems considered should be acceptable for use in the portions of existing national networks which operate to high grade performance standards. They should operate in these networks having regard for existing hop lengths, which are considered to be normally up to about 60 km. Hop lengths greate
11、r than this length, up to about 100 km, are used in special applications. An analysis of the expected performance, in therms of severely errored seconds and degraded minutes, of the system defined in this Recommendation can be found in TM4 Report (88)1* part 1. The system design must take account of
12、 interference arising from within the system, from within the network, and interference from outside the network. Methods to take account of this are given in TM4 Report (88)1* part 2, and the related specifications in this Recommendation are based on these methods. The use of space and/or frequency
13、 diversity (both in-band and cross-band) is generally considered to be necessary on large numbers of hops within existing networks, and the need for its provision, and other performance factors are discussed in TM4 Report (88) 1 *. The electrical requirements for antenna/feeder systems are also spec
14、ified in the Recommendation. . * Publication issued by: Ofice de liaison CEPT, Seilerstrasse 22, CH-3008 Berne Edition of January 30, 1989 - 2326434 000b020 2 E TIL 04-04 E Page 2 3. 3.1. 3.2. 3.3. 3,4. 4. 5. 6. 6.1. 6.2. 7. 7.1. FREQUENCY BANDS AND CHANNEL ARRANGEMENTS The systems are required to o
15、perate in the following frequency bands, to the specified CCIR Recommenda- tion on the quoted channel spacings. 4 GHz Recommendation 382.3 with 29 MHz spacing (see also Recommendation 934). The centre gap between transmitters and receivers in Recommendation 382.3 is 68 MHz. Lower 6 GHz Recommendatio
16、n 383.2 with 29.65 MHz spacing and a centre gap of 44.45 MHz. It is recommended that the alternative plan in which channels 8 and 1 operate on opposite polarisations be utilised. 7 GHz A number of frequency channelling plans are in use at 7 GHz, including that given in Report 934 Annex 5. These plan
17、s all make use of 28 MHz channel spacing with centre gaps of 56 MHz and 84 MHz. 8 GHz Recommendation 386.2 Annex 1 with 29.65 MHz spacing and a centre gap of 103.77 MHz. TYPE OF INSTALLATION Only indoor installation is considered necessary. BLOCK DIAGRAM The reference points are shown in Figure 1 (T
18、/L 04-04). These points are reference points only and not necessarily measurement points. GENERAL CHARACTERISTICS Local Oscillator Arrangement It is recommended for all bands considered that the LO frequencies for both transmitters and receivers should be arranged so that for channels in the lower h
19、alf of each half of the band the frequency is higher than the channel-assigned frequency, and for channels in the upper half of each half band the LO frequency is lower than the channel-assigned frequency. Intermediate Frequency An IF of 70 MHz is recommended. TRANSMITTER CHARACTERISTICS Output Powe
20、r Output powers in the range defined in the table below referenced to point B are recommended to be available. Range Class A Class B L 6 GHz 27 to 3O to 34 I 7GHz I 8GHz I 26 to 29 to 34 I All values are given in dBm, and include tolerances. Note. Using present technology, it is considered that Clas
21、s A output powers are achievable using solid-state amplifiers while a TWT may be required to provide the higher powers of Class B. A facility shall be available for reduction of transmit power in steps of no greater than 3 dB down at least to 20 dBm to allow equalization of receive levels. Intercomp
22、atibility between class A transceivers and intercompatibility between class B transceivers have been taken into account. Intercompatibility between class A and class B has not been taken into account. Edition of January 30, 1989 - _. 2326434 000602L 4 i f 140 MHz f 30-45 MHz TIL 04-04 E Page 3 5 dB.
23、 When subjected to this interference, the channel concerned shall respect the BER vs receiver input level specification given in item 9.2. 7.3. Spurious Emissions The levels of spurious emissions from the transmitter, referenced to Point B, are specified in relation to the requirements of the interf
24、erence model given in TM4 Report (88)l part 2. In order to establish a reference measurement for the specification of spurious emissions from the trans- mitter, a carrier wave (CW) signal shall be injected at the upconverter input to produce a measured average power at reference point B equal to the
25、 modulated input power. The specifications shall also apply when a nosmal modulated signal is applied. The limits in the following table shall be respected for individual spurious emissions. These are based on consideration of system operating with the following parameters: - Output power of digital
26、 transmitter = +30 dBm; - Output power of 1800 Ch analogue transmitter = +40 dBm; - Normal Receiver input level for digital and analogue channels = -28 dBm. Spurious Emission Frequency Specification Relative to Ch Assigned Freq. Limit Controlling Factos I LO Freq. I capacity 9.3. Interference Sensit
27、ivity O The following limits are specified: 28 29 29.65 (a) Co-channel interference sensitivity shall respect the mask shown in Figure 5 (T/L 04-04) for BERS of (b) Sensitivity to interference from one adjacent transmitter signal spaced at the appropriate cross-polar channel spacing shall respect th
28、e appropriate mask of Figure 6 (T/L 04-04). Three scales are given: one applies to the 6 and 8 GHz bands, one to the 4 GHz band and one to the 7 GHz band. These are necessary due to the slightly different channel spacings used in each band. Reference points and conditions are as in (a) above. and lo
29、p6. The receive input level and S/I ratio is referenced to point B. (c) Co-channel CW interference sensitivity. See item 9.6.2. (d) 1800 channel adjacent channel interference sensitivity. See item 9.6.2. 9.4. Distortion Sensitivity This is specified in the form of signatures using a two-path fading
30、simulator implemented either at RF or IF (if a suitable measurement point is available at IF). (a) The width and depth of the signature measured for a delay of 6.3 ns and a BER of lop3 shall not f 16 MHz relative to the channel-assigned frequency and 14 dB respectively. This limit applies for both m
31、inimum and non-minimum phase cases and whether the measurement is made with a notch approach- ing the signature from the low BER condition or from the condition where recovered carried is not synchronised. (b) The width and depth of the signature for the conditions specified in (a) but at a BER of s
32、hall not exceed f 20 MHz and 11 dB respectively. (c) In real propagation conditions notch centre frequency and amplitude may vary with time. The sig- natures discussed above are based upon static measurements and do not test the ability of a receiver to withstand this kind of variation. A number of
33、methods for assessing signature response in dynamic- ally changing conditions are outlined in section 5 of TM4 Report (88)l part 1. 9.5. Analogue/Digital Compatibility 9.5.1. Analogue System Sensitivity When using analogue and digital systems on the same hop, aspects contained in TM4 Report (88)1, p
34、art 2 section 5 should be considered. The following table gives the predicted levels of interference that would be experienced by an adjacent analogue channel at the appropriate channel spacing to a digital channel using the relevant spectrum masks of this Recommendation. It should be noted that the
35、se are calculated values only, and additive effects may produce higher noise levels than the quoted figures. 1 960 Ch 12 1800 Ch 10 1800 Ch Edition of January 30, 1989 - 2326414 0006024 T m TIL 04-04 E Page 6 9.5.2. 1 o. 10.1. 10.2. 11. 12. 12.1. The above values are derived in accordance with secti
36、on 5 of TM4 Report (88)l and assume the analogue transmitter power is 10 dB above the digital transmit power and assume that the analogue signal is modulated. The noise level produced in the appropriate inner 1800 channel analogue channel of the L 6 GHz band by the adjacent near end digital transmit
37、ter (e. g. 8-1) is calculated to be typically less than 10 pWop. When considering spurious emissions, these are limited on an individual basis to - 70 dBmO, and affected channels of an adjacent analogue channel could therefore experience interference above the quoted figure in the table. A limit of
38、-51 dBmO has been used in calculating limits for spurious signals falling outside the channel bandwidth of affected analogue channels under normal input level conditions for the analogue channel. See 7.3. Digital System Sensitivity In the case of sensitivity of digital channels to adjacent analogue
39、channel transmitted signals at either the far or near end of the hop, the effect on performance of the digital channels is less severe relative to the effect of adjacent digital channels and therefore does not require separate specification. SPACE DIVERSITY SYSTEM Differential Absolute Delay Equaiis
40、ation It must be possible to equalise up to a value of 75 ns. Diversity System Performance No specification limits are proposed in this section, but the following parameters and performance criteria are considered important and should be evaluated: (a) Response Time The maximum speed of operation of
41、 the combiner in degrees/second should be examined. This can be verified by applying a constant phase variation at one input to the combiner at an increasing rate until the combiner can no longer track the variation. (b) Main and Diversity Signal Level Difference The effect of differences between ma
42、in and diversity receive level such as arise with different-sized main and diversity antennas under normal input level conditions should be examined. (c) Combining Performance This can be evaluated by measuring the effect on the static signature. The measurement can be made with a notch of set frequ
43、ency and depth applied at one input to the diversity receiver, and a notch of variable frequency and depth applied at the other input. Diversity signatures should be examined for both minimum and non-minimum phase conditions, and for a delay of 6.3 ns. In cases of combining systems using different a
44、lgorithms depending on receiver input level, it will be necessary to perform measurements over a range of input levels. (d) Influence of Interference The effect of Co-channel and adjacent channel interference on the combiner operation should be examined, e. g. by feeding and interferer with a C/I of
45、 15 dB into either of the two receiving paths. JITTER PERFORMANCE The jitter performance should be measured on a Terminal to Terminal channel operating over the maximum permitted number of intermediate repeaters. This should include input jitter tolerance, jitter transfer function and output jitter
46、in the absence of input jitter referring to CCITT documents where appropriate (G.921 and G.823). BRANCHING/FEEDER/ANTENNA REQUIREMENTS The branching/feeder and antenna system utilised by the system must respect the following specification as measured on a real hop without any fading. Cross-Polar Dis
47、crimination (XPD) A minimum XPD of 28 dB is required. Edition of January 30, 198P ,- = 2326434 0006025 3 m TIL 04-04 E Page 7 12.2. Intermodulation Products Intermodulation products that may arise within the antenna/feeder/branching system about - 106 dBm will increasingly degrade the RSL/BER charac
48、teristic. The level of intermodulation products should therefore be carefully controlled. 12.3. Interport Isolation PI) A minimum value of 40 dB is required for each antenna (see aiso section 7.2.3.). Edition of January 30, 1989 CF I 2326434 000602b 3 O TRANSMIT BRANCHING -0- FEEDER MODULATOR TRANSM
49、ITTER 0 RF-FILTER e - - - t TIL 04-04 E Page 8 -0 _I )EM ODU LATO I E A B C D RECEIVER o BRANCHING 0 FEEDER -0 RECEIVE RF-FILTER 0 t T I MAIN-RECEIVER-PATH At Z and Z points either a 140 Mbit/s or 4 x 34 Mbit/s interface may be utilised % No filtering included. t% The connection may be made at RF, IF or baseband. Figure 1 (T/L 04-04). Transmitter and receiver block DGM. Edition of January 30- 7 - 40 - 50 - 60 - IO U 2326434 O006027 5 mi TIL 04-04 E Page 9 22.5 MHz 4,6 & 8 GHz I 31.5 MHzl 33 MHz I I I w 10 20 Frequency (MHz) 30 Figure 2(a) (T/L 04-04). Power spectral den
