1、Rec. ITU-R F.1518 1 RECOMMENDATION ITU-R F. 15 18* Spectrum requirement methodology for fmed wireless access and mobile wireless access networks using the same type of equipment, when coexisting in the same frequency band (Questions ITU-R 21 5/8 and ITU-R 140/9) (200 1) The Radiocommunication Assemb
2、ly, considering that use of wireless access systems is expanding for both fixed and mobile applications; that, for easy implementation, some wireless access systems use dynamic RF channel a) b) assignment; c) may use the same type of equipment; d) handling capability of each system; e) engineering o
3、f the radio network; that fixed and mobile wireless access (FWA and MWA) systems operated in the same band that shared use of a limited spectrum by different access systems may reduce the traffic that the traffic handling capacity of a wireless system is a basic parameter of the 0 band shared with o
4、ther wireless access systems, fixed andor mobile, is necessary, that a methodology to assess the traffic handling capability of a FWA system in a frequency recommends 1 - - - - - - that the methodology to be followed to assess the traffic capability should consider: the cell deployment schemes of th
5、e different systems; the access methods of the systems; the transmission of the interfering signal towards the victim system; the relative level of wanted and unwanted signals; the statistical distribution of activity of the systems involved; the interference mitigation techniques developed by the v
6、ictim system; 2 that the calculation methodology in Annex 1 could be used to assess frequency spectrum requirement and traffic handling capability for coexisting MWA system and FWA system using the same type of equipment. * This Recommendation was jointly developed by Radiocommunication Study Groups
7、 S (WP SA) and , 9 (WP 9B) and any further revision should be undertaken jointly. 125 2 Rec. ITU-R F.1518 ANNEX 1 A methodology to assess frequency spectrum requirements and traffic handling capability for coexisting of MWA system and FWA system in the same band using the same type of equipment, bas
8、ed on time division multiple access (TDMA) and/or frequency division multiple access (FDMA) technology 1 Introduction Recommendation ITU-R F.1402 presents the frequency sharing between a MWA system and a FWA system on condition that the interference to each other should be less than a certain level.
9、 The basic idea behind the sharing is that the FWA system and MWA system have different service areas and the examination was done to find the separation distance between both systems. In the practical operation, however, the service areas for the FWA system and MWA system - sometimes overlap and th
10、ere arises a need to coexist in part of their areas. Such coexistence is possible for the system in which the radio resource assignment is done autonomously, each equipment avoiding on-going interference. Particularly, in some cases, the MWA system and FWA system have basically different service are
11、as and share the same frequency band only in a small portion at the edge of each area, where the traffic for each system is rather small. In this situation, it is advisable in respect of the efficient use of frequencies, that the MWA system and FWA system use the same frequency band and coexist only
12、 in a small part where the service area overlaps, instead of each system using a different frequency band. Considering the above, this Annex describes the technical conditions concerning the MWA system and FWA system using the same equipment as the MWA system and accessing the same frequency band at
13、 the same area. 2 Scope In this methodology, the MWA system and the FWA system use the same type of equipment based on TDMA and/or FDMA technology, where the equipment chooses autonomously an unused radio channel within the frequency band. Coexistence conditions for such MWA and FWA systems when the
14、y use the same frequency band at the same area are examined. The method described in this Annex can be applied to a wide range of frequency bands by applying a propagation formula suitable for the target frequency. 3 References Recommendation ITU-R F.1399 - Vocabulary of terms for wireless access. R
15、ecommendation ITU-R F.1402 - Frequency sharing criteria between a land mobile wireless access system and a fixed wireless access system using the same equipment as the mobile wireless access system. Recommendation ITU-R M. 1390 - Methodology for the calculation of IMT-2000 terrestrial spectrum requi
16、rements. 126 Rec. ITU-R F.1518 3 4 Analysis of frequency spectrum requirement 4.1 Assumed system In this methodology, both the MWA and FWA systems are assumed to use the same TDMAFDMA technology and in these systems the radio channel resource assignment is not controlled by the system as a whole, bu
17、t each radio base station (MWA system) or cell station (FWA system) chooses the available resource autonomously from the candidate channels within the frequency band. It is possible that the channel being used receives interference, and in this case the system activates the interference avoidance pr
18、ocess. It is assumed that the two systems have the same functions. When the service areas of the MWA system and FWA system overlap, they can coexist in the same frequency band because the frequency assignments are done autonomously at call set up. On the other hand, when one system uses a radio chan
19、nel, the other system cannot use the channel, and in order to maintain the same call loss probability, it is necessary to assign additional frequency bandwidth. If the systems employ an autonomous frequency control method, it may be possible that different types of systems can coexist. However, the
20、interference conditions are much more complicated in this case. 4.2 Calculation of required frequency bandwidth when using the same frequency in the same service area Generally speaking, when considering the introduction of a MWA or FWA system, the frequency bandwidth necessary for the system is cal
21、culated, assuming a traffic model and arrangement of base stations or cell stations for the serving area. When considering the coexistence of a MWA system with a FWA system, the frequency bandwidth necessary to maintain the call loss probability is calculated in the same manner, and the possibility
22、of coexistence is judged. The method for such an examination is shown in Appendix 1 to this Annex. A calculation example about the coexistence of mobile PHS and PHS-FWA systems in rural areas is shown in Appendix 2 to this Annex. 4.3 It is possible to minimize the increase in the required bandwidth
23、and extend the possibility of coexistence by employing the techniques given below. Techniques for the efficient frequency use 4.3.1 Use of directional antenna It is possible to reduce the interference by using a directional antenna, not only for base stations or cell stations but also for terminal s
24、tations in the FWA applications. Several types of directional antenna, such as tilt antenna, sector antenna, array antenna, can be used. By using directional antennas, the cluster shape and size explained in Appendix 1 to this Annex will be improved. 4.3.2 Two steps of synchronization are possible f
25、or the radio signal frame synchronization for coexistence conditions. They are explained in the following paragraphs. Erame synchronization of radio signals 127 4 Rec. ITU-R F.1518 4.3.2.1 Frame synchronization within a system By using frame synchronization within the MWA system or within the FWA sy
26、stem, communication on one time slot generates interference within the system during that time slot only. Therefore, the frequency bandwidth necessary for one communication channel will be improved in non-coexistence areas when compared with the unsynchronized case. Moreover, in a TDD system, by ach
27、ieving synchronization within a system, the possibility for interference is limited to the same conditions as for the FDD system (see Recommendation ITU-RF.1402). This means that the interference between base stations, which is the most problematic, is eliminated and the coexistence conditions are m
28、uch improved. In the calculation method described in Appendix 1 to this Annex, the cluster size and spectrum requirement will become smaller than in an unsynchronized system. 4.3.2.2 Mutual frame synchronization among the systems Without mutual frame synchronization, significant interference may occ
29、ur between unsynchronized - systems, especially if base stations or cell stations are in line-of-sight of one another. In general, mutual frame synchronization will be very diffrcult if different technologies are used for MWA and FWA systems. By achieving mutual frame synchronization between a MWA s
30、ystem and a FWA system, communication on one time slot creates interference to primarily only that time slot, though it depends on how precise synchronization is achieved. Therefore, the frequency bandwidth necessary for one communication channel will be improved in all cases compared to the unsynch
31、ronized case. Moreover, in the TDD system, by achieving synchronization among the systems, the possibilities for interference are limited to the same conditions as for the FDD system (see Recommendation ITU-R F.1402). In the calculation method described in Appendix 1 to this Annex, the cluster size
32、and spectrum requirement will become smaller in all cases. 5 Traffic handling capability The simulation process in Appendix 3 assesses the traffic handling capability for coexistence of the MWA system and FWA system using the same DECT type of equipment in an allocated frequency band. 6 Acronyms DCA
33、 dynamic channel allocation DECT digital enhanced cordless telecommunications FDD frequency division duplex FDMA frequency division multiple access FWA fixed wireless access MWA mobile wireless access 128 Rec. ITU-R F.1518 5 PHS personal handy-phone system PSTN public switched telephone network TDD
34、time division duplex TDMA time division multiple access APPENDIX 1 TO ANNEX 1 Calculation method 1 Coexistence model in calculating the necessary frequency bandwidth, the coexistence model shown in Fig. 1 is assumed. FIGURE 1 Coexistence model Service area for FWA Coexistence area FWA cell station a
35、rea / ciuster area MWA base station area Note I - The service areas for the two systems may be identical. Noie 2 - Cluster radius for the two systems may be different. 1518-01 129 6 Rec. ITU-R F.1518 1.1 Radio base station model and cluster area 1.1.1 Radio base station model In this model, MWA base
36、 stations and FWA cell stations are deployed in the same service area and use the same frequency band. The two systems are based on the same system and use the same carrier assignment and the same access method. When a system uses a radio channel, the other system cannot use the radio channel and ma
37、y experience interference on the immediately adjacent channels. The FWA cell station covers a circle area with radius r- and the MWA base station covers a circle area with radius r,. Each base station is scattered uniformly in the service area. Each base station can use any unused radio channel in t
38、he frequency band, without any other restrictions. 1.1.2 Idea of cluster area - To calculate the frequency reuse conditions in such a case, a virtual “cluster area” is assumed. This cluster area is assumed to exist uniformly within the service area and it is assumed that the same frequencyhime slot
39、combination cannot be reused in the same cluster area, but can be reused in a different cluster area. 1.1.3 Calculation of cluster area radius We assume that there are two circle areas A and B which have the same radius, r, and border on point P as in Fig. 2. Area A is assumed to be the interfered a
40、rea and area B is assumed to be the interfering area. Among the interfered baseke11 station areas in area A, we pick up the worst basekell station area C that borders on point P. BaseIcell stations and subscriber stations are scattered at various points in area B. So, the received power from an inte
41、rfering radio station in area B at point P is not uniform. But if we use an average value, the received power is about the same level as when the interfering radio station is at the centre of area B. In addition, in order to simplify the problem and to assume the worst-case scenario, we assume that
42、the subscriber or basehell station has the maximum antenna gain toward point P. Similarly, subscriber stations are scattered at various points in baseke11 station area C. But if we use an average value, the received power at point P is about the same level as when transmitting radio station is at th
43、e centre of area C. Considering this way, it is reasonable to suppose that at point P, the DIU is given by the following equation: DIU = Prc/PrB() where: D : desired signal level U : Prc : PrB(r) : r : undesired or interfering signal level received power at point P from transmitting radio station at
44、 the centre of area C received power at point P from interfering radio station at the centre of area B radius of areas A and B. . 130 Rec. ITU-R F.1518 l 7 Therefore, the cluster area radius, rc, limited by the following equation: FIGURE 2 Calculation of cluster area radius 1518-02 1.2 Traffic model
45、 It is assumed that subscribers are scattered uniformly in the service area, the subscriber density of the MWA system is Um, and that of the FWA system is UJ the traffic per subscriber for each system is am, afrespectively, and that the required loss probability is bm, bfrespectively. In the followi
46、ng calculations of the required frequency bandwidth, only ordinary speech telephone calls are considered. 2 Calculation target area In calculating the required frequency band, the area for calculation target, which is called calculation target area, is determined first. FWA systems are often used as
47、 a complement system for wired access system. In this case, the FWA service area is a closed area, for example an area of several-kilometre radius, where the houses are located. The different service areas are independent in terms of radio propagation because they are widely separated, or there are
48、some geographical conditions that prevent the radio propagation. Such closed area is called closed service area. Taking this into account, the calculation target area is expressed as follows: Calculation target area size, sc = min. (closed service area size, cluster area size) (3) where min. (u, b):
49、 the smaller value of a and b. In ordinary cases, the MWA service area may be the same as the FWA service area when the area is closed service area. In the following calculations, it is assumed that the calculation target areas for the MWA system and FWA system are the same (see Note 1). 131 8 Rec. ITU-R F.1518 NOTE 1 - Calculation when the calculation target areas for the MWA system and FWA system are not the same is for further study. 3 This calculation assumes only that a single MWA system and a single FWA system coexist, but could be extended to include multiple systems. When th
