stds-802-16: sub10. The importance of good performance in multicell

[vicente.quilez_sanchez@alcatel.es]

     a)Why Interference-limited and Multicell?
     
     Very likely IEEE 802.16sub10 will have to face solutions for wireless 
     point-to-multipoint public applications, targeting at SoHo and 
     high-end residential users, as well as for point-to-multipoint private 
     applications targeting at corporate users and campus LANs for the 
     provision of mainly data traffic.
     In particular the location of SoHos and high-end residential users 
     likely correspond to urban and suburban environments (much more than 
     in rural environment), which implies difficult radio propagation 
     conditions (derived from distinct multistoreyed buildings hights,etc), 
     and thus not very long radio hauls. As in practical terms, Line Of 
     Sight (LOS) is required to secure suitable BERs for QoS data 
     transmission, and the coverage penetration with respect to the 
     customer population must be as high as possible, the consequence is 
     that multisites will be required.
     Another analysis reinforcing the idea of multicell comes from the fact 
     that, as Internet applications evolve, the requirements of peak bit 
     rates will increase along time, thus the provision of several Mb/s per 
     user will likely be required, and that will imply more efficient 
     modulation techniques (several bits per Herz), which in turn implies 
     difficult constellations and therefore higher figures in the C/I 
     ratios. This means shorter radio hauls and higher influence of the 
     interferences sources. 
     Based on all the above, these systems will have multisite 
     architectures and will be limited by interference (rather than by 
     noise or by coverage)
     
     b)-Consequences of good performance in interference-limited multicell 
     scenarios:
     
     For any wireless system to behave properly in these conditions, it is 
     essential for the system to have a sort of dynamic resource allocation 
     scheme that can react in real-time and make the most efficient use of 
     the available pool of radio resources (i.e. radio channels). More 
     efficient use means in this context to chose those radio resources 
     which have the best radiolink quality (i.e. those with the minimum 
     amount of interference). It is understood that for a packet-based 
     wireless system (which is the obvious technical choice when dealing 
     with bursty data, such as Internet traffic), the interference map 
     changes very quickly, with multiple radio resources being requested or 
     released in a very short time. Thus automatic, real-time operation, is 
     key in this context.
     A real-time dynamic resource allocation scheme will provide three main 
     advantages: 
     1-It will preserve a good performance for the systems in multicell 
     scenarios, keeping capacity figures per site in multicell close to the 
     capacity figures obtained for isolated cells
     2-It will  keep the frequency reuse factor close to one, that is, it 
     will preserve spectrum efficiency
     3-It will probably allow frequency planning avoidance, which will 
     greatly simplify network planning, a key characteristic throughout the 
     deployment life cycle
     
     c) Conclusions
     
     Based on the reasons mentioned above, it is proposed that good 
     behaviour in interference-limited multicell scenarios be considered as 
     a key requirement for future IEEE 802.16sub10 standard
     
     It is also advisable for IEEE 802.16sub10 to incorporate a sort of 
     real-time dynamic resource allocation scheme.
     
     
     Vicente Quilez
     Alcatel
     veq@alcatel.es