July 20, 2006

Summary of Various Recent HPWREN Routing and Topology Updates

Several changes have recently been made toward HPWREN improvements and increased connectivity.

Routing interconnectivity with the Tribal Digital Village Network (TDVNet)

A July 2005 article regarding continued collaboration with Native Americans details current activities of re-interconnecting HPWREN with TDVNet. Specifically, the HPWREN team worked with the TDVNet team to add a small router to their tower site in the Mesa Grande area since the time of the article. The objective is to facilitate distance education programs between TDVNet and HPWREN-connected sites, while making non-routeable address space of both systems reachable via the interconnection router. TDVNet continues to be an excellent partner for the mutual interests of the Native American community and HPWREN.

Direct routing with the San Diego State University campus network

Similarly, with great help from the SDSU campus networking group, non-routeable HPWREN address space is now directly accessible from the SDSU campus network. HPWREN currently has three network address spaces:

  • a very limited number of world-routeable IP addresses
  • address space that is only routeable with in the HPWREN network
  • address space that is directly reachable from TDVnet, SDSU and UCSD

Upgrades to the San Clemente Island connectivity

Installed in 2002, the original 2.4 GHz 72-mile HPWREN link between UCSD and San Clemente Island has been upgraded to 5.8 GHz Trango Atlas OFDM radios - using relatively small two-foot (at UCSD/SDSC) and four-foot (on SCI) antennas. Nevertheless, the connection is able to exceed a 10 Mbps throughput! This upgrade enables new applications beyond the current seismic sensor and weather station telemetry data that utilized the 2.4 GHz link.

In addition, as part of a collaboration between SPAWAR and HPWREN, an experimental link was created between SPAWAR's Point Loma site and an additional site on San Clemente Island. The photo to the left shows the antenna at SPAWAR being crane-lifted onto a building-top. A further antenna was used to connect the site to the HPWREN backbone node at Mount Soledad. The links utilize 5.8 GHz Redline AN-50 OFDM radios, with the SPAWAR to SCI link running a NAVY link on the opposite antenna polarization. This setup is still being debugged, as, despite significant channel separation, the two links interfere with each other. However, on a single polarization the TCP throughput with the AN-50 radios via the large antennas has been demonstrated as being able to exceed 20 Mbps.

In the above experimental setup, non-OFDM 5.8 GHz Interwave/YDI/CX radios were tested as well - using the same eight-foot antennas, but were unable to sustain the link during testing. This appears to demonstrate that OFDM is a more suitable technology than conventional radios for long links across water.

Point Loma connectivity via the UCSD Hillcrest Hospital

Another activity was the replacement of the San Diego Coastal Ocean Observing System (SDCOOS) 2.4 GHz link between Mt. Woodson and Point Loma. Facilitated by a collaboration with the San Diego State University and the UCSD Hillcrest hospital, this activity created a 5.8 GHz Trango Atlas link between SDSU and the hospital roof. A further link, currently using 5.8 GHz TrangoLINK-10 radios, is connected to a facility which SDCOOS is utilizing at Point Loma.

Additionally, discussions with the National Park Service are underway regarding possible collaborations at the Cabrillo National Monument (CNM). This involves the potential use of a tower near CNM, for which the plan is twofold: 1) upgrade TrangoLINK-10 radios to Atlas and 2) connect CNM and the SDCOOS via the tower.


The links are between SDSU (left), via the UCSD Hillcrest hospital roof (top, with a view towards SDSU), toward Point Loma (right, taken on top of the hospital roof).


Current and future: Major additional changes are planned, especially with the HPWREN backbone itself, which includes transitioning the backbone to all-licensed links, and upgrading some high-demand links to 155 Mbps (OC3-class) capability. These upgrades requires finishing the FCC-license process, which has been difficult due to the lack of radio spectrum availability in southern California.

Please note: The product names used in this article are only meant to show some examples, and are not intended as an endorsements of product suitability for any applications.

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