Fall 2008 Issue

HSMM

New High-Speed Multi-Media Radio Mesh Networking

By John Champa, K8OCL

If you have not been tracking the events of the North Texas Microwave Society (ntms-hsmm@yahoogroups.com) on the HSMM web page, you are missing a lot of action! The NTMS is in the heart of wireless Telco development country in the Dallas/Plano area. New developments and innovative thinking are taking place all the time.

de KD5MFW

For example, recently I had an opportunity to interview Glenn Currie, KD5MFW, who is working with a team of HSMM radio experimenters in the Round Rock (Austin), Texas area. This team is called the Austin HSMM Special Interest Group (SIG). There are some key participants from the Roadrunners Microwave Group (RMG).

An interesting development Glenn reports is that by using Optimized Link State Routing Protocol (OLSR) their new mesh nodes auto link and are passing data within five seconds of coming into RF range. For more information on OLSR, go to <http://www.olsr.org>. With a large mesh, when two nodes are passing data and a node in the link goes down, OLSR automatically switches to another route through the mesh. The user usually notices nothing. This development puts HSMM on the cutting edge of mesh networking!

Figure 1 is a web page served up from inside the WRT54G router running the Austin HSMM SIG version of the OLSR mesh software. Under “Links” are shown all the current nodes within RF range. These nodes include node 71, which is serving up the web page (10.1.71.1:1978). Port 1978 is the OLSR status port address for each node.
Moving to the right on the top section, local node 71 can see remote nodes 207, 150, and 48. There is no delay (hysteresis) set. RF link quality between all nodes is “perfect = 1” except for node 71, which has a less than perfect, but usable, link to node 48, and thus the 0.90 rating. It looks as if that 0.90 link quality was because one packet was lost out of the last ten (but was resent and correctly received). Therefore, the net link quality to all nodes is perfect = 1.00, because no data was lost, although a resend was needed from node 48. The next group of data shows an IP address that node 71 can see. SYM, MPR, MPRS explanations will not fit in the caption.

Willingness shows the number of possible ways a node has to get to other nodes. Two Hop Neighbors show the IP address of the two different hops a node can make to other nodes. You have to click on the down arrow to see the addresses. In a big network the list would be huge.

The Topology entries show all combinations and permutations of links between nodes in the network: LQ, ILQ, and EXT all are measures of link quality.

Link quality is important for such things as Voice over Internet Protocol (VoIP). If the link quality is poor, you may be able to sputter files through without errors, but there will be dropouts for VoIP or video. No user intervention is needed to link with the mesh. This is why it is good for the field—no messing with addresses in the field. Exciting stuff! I will report more details on that in the next column. I also will try to strike a careful balance between giving recognition and at the same time protecting developers’ time by preventing them from getting swamped with questions, which could interfere with their part-time work.

It appears that the Austin HSMM SIG is way ahead of what most other groups are doing in HSMM. John, N5OOM, and the crew in the North Texas Microwave Society HSMM SIG have done a lot of good work, and John’s presentations are well done and informative. Some of that material has been published here, and I highly recommend it to people interested in HSMM. However, nothing has been published yet about crystal modifications to the WRT-54G or making serious modifications to the firmware. We are looking for material on those subjects.

Glenn promotes HSMM for several reasons. Hams need to make use of the inexpensive WiFi gear that can easily be operated on the ham bands and get into broadband computer-based radios. Hams need to be active in this or the hobby will fade. It is related to what the younger tech folks are doing with the internet.
Glenn grew up with computers and radios. He has one foot in each camp, as do all the key developers he is working with. That puts them in a position to have just the right perspective to see the great value of HSMM and how it needs to come together. Glenn has a 16-GB USB thumb drive on a lanyard that he carries around with him. It is full of academic papers related to the U.S. Department of Defense’s Defense Advanced Research Projects Agency (DARPA) and other robot and communications topics, and the material they have collected on their HSMM projects. I hope to convince him to publish some of that material in future columns.

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