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Taking coax [networking] to the max

Sat, 12/31/2005 - 7:00pm
Gary Langille, Systems Engineer, EchoStar Technologies Corp.; Chairman, MoCA Field Test Working Group

The Multimedia over Coax Alliance (MoCA) performed field trials in 246 homes across the U.S. and successfully validated that the technology, for its initial specification, meets and exceeds the MoCA requirements for multimedia home networking. Several members of MoCA—Comcast Corp., Echostar Communications, Entropic Communications, Linksys, Motorola, Panasonic, Radio Shack, and Toshiba—performed testing in their respective areas resulting in tests of homes in more than 120 zip codes.

Figure 1

The key results measured and verified in the field tests were:

  • Packet error rate less than 1E-6.
  • Latency less than 5ms.
  • Net usable (MAC) data rates, with no changes to the home coax system:
    • 97% of all paths in all homes achieved > 100 Mbps.
    • 100% of homes achieved > 120 Mbps on at least one path.
    • 90% of homes achieved > 80 Mbps on every path in the home.
  • Net usable (MAC) data rates, with simple remediation to the installed coax cable system:
    • 100% of homes achieved > 95 Mbps on every path in the home.

The results show that the MoCA technology supports the advanced multimedia requirements and coexists with existing services on the coax while operating in the 1000 MHz to 1400 MHz band. The test results cited in this document are averaged across the 1000 MHz to 1400 MHz band. The most important parameter for both the field testing and multimedia home networking deployment is throughput, or net usable (MAC) data rate. The throughput and PHY level bit rates measured in the field tests are shown in the curves in Figure 1.

MoCA requirements

The MoCA marketing requirements document (MRD) sets forth technical and general requirements for in-home networking of high-definition multimedia, audio, voice and broadband data. Each MoCA member contributed to the development of the MRD and the result was approved by MoCA's board of directors. The MRD includes comprehensive performance, quality of service (QoS), and general requirements. A summary of the major requirements includes:

Performance
  • >100 Mbps net usable (MAC) throughput in > 95% of homes.
  • >80 Mbps net usable (MAC) throughput in 100% of serviceable coax outlets with reasonable remediation such as replacing low bandwidth splitters; installing in-line filters, diplexers, or amplifier bypasses; or point of entry (POE) filters onto the in-house coax. Note: a serviceable coax outlet is one that supports analog or digital TV service and/or DOCSIS.
Quality of service
  • Must support eight 802.1p priorities.
  • Latency: <10 ms for highest priority asynchronous traffic up to the maximum aggregate throughput.
  • Packet error rate: 1E-5 at any throughput.
General requirements
  • Support tree-branch, loop (or daisy-chain), and home-run in-house coax topologies.
  • Self-adaptive to time and location varying characteristics of coaxial networks.
  • Plug-and-play at the majority of serviceable coax outlets in homes with no need to access or change splitters, or run new cables. For serviceable coax outlets that are not plug-and-play, there shall be a reasonable remediation/corrective method, such as replacing low bandwidth splitters; installing in-line filters, diplexers, or amplifier bypasses; or POE filters onto the in-house coax.
  • Compatible with existing devices on the coax with no interference.
  • Compatible with existing services on the coax with no interference.
Testing methods

Testing was conducted in accordance with a Field Test Plan developed by the MoCA Field Test Working Group (FTWG) and approved by the MoCA board of directors in advance of the testing. The test plan included basic and advanced testing procedures for field tests and a comprehensive battery of lab tests for requirements inappropriate for field measurement. Basic testing in homes was done in a plug-and-play manner, without any changes to the home, and often with non-technical homeowners doing the testing. Additionally, technical personnel conducted advanced testing in a limited number of homes. The advanced tests included the basic testing procedure followed by detailed measurements and modifications to the in-home coax.

In-home testing was coordinated by Field Test Coordinator(s) (FTC) from each MoCA member. The FTCs were responsible for recruiting, training, and scheduling testers, maintaining the test system, and uploading test results following each test. Testing was performed independently by technical and non-technical volunteers employed by MoCA member companies. Test homes included single-family homes, apartments, and condos and were required to have at least three coax outlets.

All tests were performed using a field test kit developed by the FTWG. The kit allowed each tester to install MoCA devices in their home at up to four coax outlet locations, continue operation of their cable or over-the-air services to their installed set-top boxes, TVs, VCRs, PCs, etc., and to simultaneously run data transmission tests over the MoCA network. During each test, the MoCA signal was automatically varied in transmission power and frequency of operation to characterize performance on each path being tested in the home. Test data was uploaded at the conclusion of each test to an independently maintained site. Data files were then validated prior to inclusion in the database of test results. In cases where the test results seemed anomalous, the site was revisited and retested by either the volunteer, the FTC, or trained personnel. During the revisits, the tester tried to ascertain and document the reason for the original anomalous results.

Figure 2
The data was collected from all tests, analyzed and plotted to yield statistics. Because the field test kit consisted of prototype hardware and test software, some defects were found that resulted in updates to hardware and software to eliminate bugs or inconsistent operation. Each change to the hardware or software was analyzed against the test data to determine if a home required retesting. If so, the home was retested and the new data for the home was substituted into the database of collected data. Additionally, there were errors introduced from some volunteer testers such as connecting the test unit to a coax output connector on a VCR or the like, neglecting to power on one or more of the test units, or neglecting to connect the coaxial cable at all. In these cases the tests showed invalid results that were corrected with a simple retest of the home using the correct procedures. The invalid data for the home was replaced with the valid data in the results database.

When an advanced test was performed in a home with multiple cable drops, the multiple drops were connected with a standard 4:1 splitter as specified by the test plan prior to testing. During basic testing, some multiple drop homes may have been tested by volunteers unaware of the multiple drops. In such instances, the results were included in the statistics.

Test home statistics

Figure 3
Tests homes were located in and around areas where MoCA members have facilities. A summary of the general areas or counties of the test homes is provided in Figure 2. Note the wide geographic dispersion of the test locations.

Along with the locations of the homes, the volunteers and FTC's were asked to collect specific data on the coaxial cables in the home, the equipment installed in the home, and the services provided on the coax. As noted earlier, homes were generally qualified by having three or more coax outlets. However, in a small number of homes, only two of the outlets were connected. Figure 3 shows the distribution of coax outlets found in the test homes. It is worthy to note that over half of the homes tested had four or more coax outlets in the home.

Conclusions

The primary goal of the MoCA Field Test was to validate that the proposed MoCA technology would meet or exceed the requirements established by MoCA for home networking of digital entertainment in a real-world environment. The tests conclusively show the technology consistently exceeds the requirements in real-world homes and coax configurations as represented by the wide range of locations and homes tested.

Figure 4

E-mail: info@mocalliance.org | www.mocalliance.org

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