re: Rysavy articles on GPRS.
Peter Rysavy of Rysavy Research has written extensively on the topic of mobile data communications. I've quoted or linked several of his articles in the past.
There is not a lot of hype in his articles ... and he has never romanticized anticipated throughput.
Here are links to several he has written on GPRS as the standard evolved (updates previous links some of which are broken):
* Clear Signals for General Packet Radio Service (Network Magazine, December 2000)
rysavy.com
* The Road to a Wireless Future (October, 2000, Network Computing) - 1x discussed also
* The Evolution of Cellular Data: On the Road to 3G (1999, for Intel) - 1x also
rysavy.com
* General Packet Radio Service (GPRS) - (1998, for GSM Data Today)
rysavy.com
also - his wireless roadmap seems reasonably accurate:
img.cmpnet.com
Selected excerpts from his latest GPRS article:
>> As for speed, you'll see figures quoted all over the map, because operators can flexibly deploy GPRS. Though GPRS' maximum theoretical rate is just over 160Kbits/sec, operators will initially offer speeds in the 26Kbit/sec to 52Kbit/sec range. Although not blazing fast, this speed compares to the speeds road warriors are used to, and works for many applications. QoS will enable applications to specify items such as throughput, latency, and reliability, but don't expect much emphasis on QoS in initial rollouts. Rather, think of QoS as a key feature for enabling future wireless multimedia applications, such as voice and video.
Another enticing aspect of GPRS is global coverage, though this will be more of a reality in Europe and Asia, where the underlying GSM cellular networks are much more dominant. Nevertheless, with VoiceStream emerging as a strong nationwide carrier in the United States, most U.S. users will be able to subscribe to GPRS services. Once operators have GPRS roaming agreements in place and multi-frequency devices become available, users may eventually access GPRS services in over a hundred countries. (Note: articlee written before AWS announced their GPRS move).
Theoretically, a user could have all eight time slots in the radio channel, but carriers are likely to limit the number of download slots to four (or fewer), for a maximum of 52Kbits/sec, and the number of slots available for uploads to one, for a maximum of 13Kbits/sec. The principal reasons for limiting the number of time slots are to reduce the device's power consumption, temperature, and cost, and to increase the number of simultaneous users the network can support.
If you think GPRS will become obsolete once third-generation cellular rolls out, think again. Data services for Wideband Code Division Multiple Access (CDMA, the 3G version of GPRS) use an evolved set of GPRS protocols and infrastructure. In fact, cellular standards groups have already defined how voice itself could just become another IP application over GPRS in 3G networks. CDMA networks (utilized by SprintPCS and Verizon) employ a different wireless data architecture, which is outside the scope of this article. But, given GPRS's worldwide dominance, GPRS will be this decade's key wireless data technology.
Two other prominent wireless technologies are Bluetooth and WAP. Both have an important relationship to GPRS. ..... So, will all GPRS applications use WAP? Absolutely not. Users can consider GPRS for any IP-based application, so long as the application isn't too bandwidth-hungry. Nevertheless, GPRS carriers are looking to GPRS as a key enabling technology for WAP because GPRS offers the perfect always-on, always-connected transport for WAP.
GPRS could quickly become a victim of its own success if too many people use it for large downloads. Since users contend for a limited number of GPRS radio channels, throughput will go down with an increasing number of active users. WAP addresses this issue by a text orientation and small screens, thus minimizing the network's load. Carriers are likely to push WAP over GPRS vs. general-purpose networking.
GPRS not only has a bright beginning but also has a bright future with a comprehensive evolution path. The first option carriers will have to enhance GPRS is adding new coding schemes that increase rates to 15Kbits/sec or 21Kbits/sec per time slot (up from the current data transfer rate of 13Kbits/sec). These new coding schemes reduce the amount of forward error correction, and so require a strong signal.
The next stage for GPRS is even more interesting. Though originally intended as a data service operating parallel to voice services, standards groups are defining how GPRS will be able to support voice services using Voice over IP (VoIP) protocols. ..... an end-to-end approach for multimedia over IP will enable many new kinds of applications, and promises to reduce the cost of core networks for carriers. <<
- Eric - |
