December 2008 Archives

Performance of Cellular Data Networks

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We tested performance (delay, uplink throughput, downlink throughput) and availability (percentage of tested locations with service with the advertised service area) for ATT (Cingular), Sprint and Verizon cellular data networks in a number of North American cities during the NWBR. We tested one or more of these networks in these cities: Anaheim CA (2x), Brookline MA, Chico CA, Cupertino CA, Daytona FL, Eugene OR, Galt CA, Longmont CO, Madison WI, Minneapolis MN, Mountain View CA (2x), Palo Alto CA, Philadelphia PA (2x), Portland OR (2x), Raleigh NC, Rochelle IL, St. Cloud FL (2x), Santa Clara CA, Sunnyvale CA, and Tempe AZ (2x). In several cities we tested twice to detect changes in traffic and improvements in network service. Great disparity of service was noted with several small towns (Galt CA and St. Cloud FL) having no 3G service at all (and hence barely averaging 100 kpbs of data service) from any service provider while larger, growing metro areas (Tempe AZ) had an abundance of high performance cellular data providers (with downlink service approaching 1000 kbps). When available, the three major cellular providers offered a similar grade of performance averaging about 200 kbps on the uplink and about 500 kpbs on the downlink. No measurements ever exceeded 1000 kbps.
Network Delay (msec) Uplink (kbps) Downlink (kbps) Total Availability 3G Availability
ATT (Cingular) 318 195 473 75% 59%
Sprint 330 215 559 96% 90%
Verizon 366 179 494 92% 70%
Average 340 195 507 89% 73%
On average, Sprint offered the highest performance with the greatest availability. ATT and Verizon both offered a slightly poorer grade of performance but the availability for these two networks is far more interesting. Cellular networks do not offer a single grade of service ... where available, 3G service is offered but when there is no 3G capacity left, the networks fall back to offering 2G service instead. This fallback results in an almost 3x decrease in upload performance and over a 5x decrease in download. For Sprint, almost all our testing locations offered 3G service and only in 6% of the those locations did the offered service fall back to 2G. For both ATT and Verizon, in about 25% of the locations with service - we could not get 3G service but rather fell back to 2G service. And in the case of ATT, this exacerbated the already poor availablity with only 75% of the tested locations could we get service at all! As we will see when we look at the results for WiFi networks, with the proper client modem selection, WiFi network uniformly outperform and can achieve availability of 85% - not dissimilar to the average availability of 89% for cellular data.