thoughts on coexistance cognitive WiMAX

802.16h focused only on coexistence of WiMAX in the unlicensed bands. It is not really a fully cognitive application.

Berleman paper talked about techiques for how 802.16 can block out competing 802.11 radios in the same spectrum. Because of 802.11's reliance on listen-before-talk MAC the WiMAX is able to block out 802.11 as needed by making it's tranmissions longer than the contention period for 802.11. This in effect does not allow the 802.11 to transmit when the 802.16 wants to. Of course this is a totally unfair type of methodology.

Possible similarilty between 802.16 coexistence and 802.11e in terms o fthe hybrid controller and sharing a single frequency channel in the time domain.

802.22 will use coexistence beacons to help with self coexistence of multiple Base Stations in the same area.
-Coexistence beacons will be time stamped, CPE from neighboring networks may be able to overhear the beacons. They will be looking for them to be able to help inform their own basestations of potential hidden nodes that the base might not be able to see

Currently a WimAX deployment requires significant planning for frequency reuse strategies. The Base station coordiantion of large scale deployments is similar to cell phone type deployments. While this is an acceptable and almost required deployment strategy for North America what about in highly rural and depressed 3rd world countries. Or in areas where countries are bordering with each other.

It is highly unlikely that you are going to be able to enable such a strong coordination between base stations. More likely is that you are going to have people just setting these up without knowledge of the other Base stations in the area. Licenses may be granted for a particular area by a country but these will be invalid when you are on the border of another country.

Cognitive WiMAX would lend itself to an automated initialization sequence upon powering up. This enables a low level of skill to be required for the design and deployment of a network which lends itself to a 3rd world type deployment. A base station and accompanying CPEs would be able to start up and sense the environment in terms of frequency availability and potential interference. based on this knowledge it can change it's PHY setup to accomadate the current environment.

Question, if a Base station is constantly sensing and decides to change frequencies than it will have to tell all the CPEs but what happens if a new CPE turns on but doesn't know what frequency the Base is on. In current WiMAX the frequency is fixed and the CPE knows where it needs to be to find the base station. In this type of case, the CPE is going to have to go through a search mechanism for scanning the potential frequencies that a base station would be on until it finds it.

Current WiMAX is a narrow profile compared to what the 802.16 standard is capable. This was required to develop synergy among vendors and to solidify a development plan and create more economy of scale for the development of WiMAX.

A cognitive WiMAX would be a very flexible radio, capable of changing its frequency, power and range, and other variables to accomadate the desired operation and the wireless ecosystem in its surrounding area.

The 802.16 MAC structure has an inherent weakness in that it is based of a scheduling system coordinate by the base station. there is no listen than talk of like 802.11. The WiMAX will provide higher quality of service and more efficient bandwidth but if there is enough noise or interference to block the preamble and the DL/UL scheduling there might be problems.

frame based 802.16 MAC requires significant rigourous protection