802.16j: WiMAX For WiMAX Backhaul

One of the main OPEX (operational expenditure) drivers in mobile networks today is the requirement to connect each base station directly to the network. In most cases this means installing a cable or microwave connection at each base station site. For fixed line connections, UMTS/HSPA base stations mostly use a number of E-1 or T-1 links today, each being capable of transmitting about 2 MBits/s. With rising bandwidths, however, using several E-1 links for each base station will soon become difficult for both cost and availability of wires. Alternatives are fiber or using a transmission technology which can get more out of a pair of copper cables. Nevertheless, it will remain expensive.

For WiMAX networks, the IEEE has started in 2006 to work on 802.16j "Mobile Multihop Relay" (MMR). The basic idea behind MMR is to allow WiMAX base stations which do not have a backhaul connection to communicate with base stations that do. On the one hand this will of course reduce the bandwidth  available to users in the cells involved in relaying packets. On the other hand it’s an elegant way to save costs and extend network coverage into areas where connecting a base station directly to the network via a fixed line connection is economically or technically not feasible.

Here are some ressources with more information:

4 thoughts on “802.16j: WiMAX For WiMAX Backhaul”

  1. Hey Evert,

    yeah, it’s a bit like Mesh but it sounds like it’s not self organizing. If I remember right there was sort of a Mesh approach already in the first version of the WiMAX spec before 802.16e was born which also included CPE’s. Looks like this approach now is only for base stations and geared towards making sure mobility features are also supported across base station nodes which use a WiMAX backhaul link.


  2. Hi,

    Yes, almost true 8). I’m currently working in this standardization process at Siemens. There are different kinds of relays, and here you talk about range extension fixed ones.

    There’re also throughput enhancement relays that are placed in the cell, where the coverage is poor and as result only low bit-rate modulations like QPSK can be guaranteed. Relays increase signal so that 64QAM is used and as result higher data rates are achieved. In average in such systems bandwidth can be utilized even more eficciently than in one-hop transmissions, depending on how smart the deployment is done 8)

  3. HI All! I find quite interesting this discussion regarding the future enhancements introduced with .16j amendment. Could someone, please, suggest some useful links where to find status of current implementations as well as some good tutorial regarding the multi-hop relay tech itself?

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