Clark, engineer, or anyone,
What about HDR? Any deployment is going to implement this HDR? I know it is going into trial with Chase Tel.
Find the following from CDG site:
"Wide scale
While Sprint will start delivering data on a wide scale during the first quarter of 1999 at 14.4 kbps, it plans to move as quickly as possible to a platform that will deliver data to mobile users at 64 kbps and over fixed links at rates of hundreds of kilobits per second in the near term.
Maddox says Sprint's wireless data agenda dovetails with the company's local access strategy on the wireline side, dubbed Interactive On Demand Network (ION), where voice and data combined over IP provide support for seamless integration of a variety of services.
PCS operators employing CDMA technology have a big competitive advantage when it comes to allocating extra bandwidth to data, given the efficiencies they're enjoying on the circuit-switched voice side, notes Jeff Belk, vice president of subscriber marketing at Qualcomm.
The company's research shows that these carriers are currently using between two and four of their 1.25 MHz channels for mobile services in any given market, leaving in excess of 20 MHz of spectrum for use in new applications, including fixed voice and mobile and fixed data services. "There's plenty of bandwidth to work with within the existing spectrum allocations when it comes to putting 3G-type [third generation] applications into play," he says.
But, while the latest generation of base stations coming on line from the leading CDMA vendors all support IS-95 in the circuit-switched voice domain, they are taking disparate paths in the evolution to ever higher speeds on the packet-switched data side.
The emphasis within the CDMA vendor community a year ago was on completing the IS-95B specification, which would allow operators to implement 64 kbps data access over the 1.25 MHz channels of their existing infrastructures via software upgrades without having to change hardware. This is supported by Motorola.
"By providing operators [with] an upgrade to the IS-95B technology, we can supply them with some of the same high-speed data applications that 3G will offer, all through a simple software upgrade to their existing CDMA equipment," says Moe Grzelakowski, corporate vice president and general manager at Motorola CIG's Cellular Systems Group.
An alternative data transition option being adopted by Nortel is the cdma2000 Basic system, which has supplanted IS-95B as a bridge to third generation applications because it offers support for four or five users at 64 kbps, or perhaps even 144 kbps, per 1.25 MHz carrier. Nortel plans to provide cdma2000 Basic products some time over the next 18 months, but will require new application-specific integrated circuits (ASICs) in the base stations, representing "about 20 per cent of the infrastructure on the ground", not to mention support from terminal suppliers, says David Murashige, vice president for CDMA marketing and management at Nortel.
Lucent is taking still another approach by leaving the base station alone but requiring a change in radios, according to Cindy Christy, vice president of Lucent's AMPS and PCS business. This can be done because Lucent's new base transceiver stations come with ASICs that can be programmed to support higher-speed data throughput over multiple 1.25 MHz carriers, essentially allowing three 1.25 MHz streams to be fed through a 5 MHz radio, which is the channel capacity envisioned for full 3G systems.
"We're proving that third generation radios can indeed coexist with today's 2G systems, thereby preserving the investments our customers have made in cdmaOne," Christy says. "The technology will enable incumbent operators as well as new licensees to offer two tiers of service from a common network platform, depending on customer demand for bandwidth."
Qualcomm has come up with still another approach which, if successful, could radically alter thinking about third generation technology. Rather than relying on a "nailed-up" access rate such as 64 kbps for a set number of users per channel carrier, Qualcomm's new high data rate (HDR) technology exploits the bursty nature of packet communications, creating a contention-based access system. The trade-off is a decrease in per-user throughput from a peak of 2.4 megabits per second as ever more users come on the channel, resulting in typical access rates in the range of 1.25 to 1.5 mbps according to the vendor.
No compromise
"It's like Ethernet but without collision, which means you can support a lot of users," Jacobs says. Unlike 3G systems, which are designed to support voice and data access over the same 5 MHz channel, the HDR system requires that one or more of the IS-95 1.25 MHz channels is allocated to data only.
This is a better way to maximize data efficiency, Jacobs asserts. "With data you can burst out packets at very high rates and pass around access [to time slots] to multiple users," he says. "You don't have to compromise data efficiency the way you do when you share the channel for voice and data."
Qualcomm demonstrated the new system at the recent PCS '98 convention in Orlando, using upgraded versions of its IS-95 base stations. The company used FPGA (field programmable gate array) circuit boards or "emulators" in lieu of ASICs, which it anticipates will be ready for support of HDR upgrades in field tests by mid-1999, with commercial rollouts by the end of the year.
First, however, Qualcomm must find partners to license the technology, including handset and other terminal suppliers, none of which have stepped forward publicly to offer support for HDR. "There are obvious complications with a proprietary new air interface specification when you don't have any sense of how much support there's going to be," Nortel's Murashige notes, adding that the company hasn't "closed any discussions on HDR with Qualcomm".
The options in the evolution to data may be varied but they won't stand in the way of operators deploying new base stations. The good news is that all the leading suppliers have come up with new base stations that address a wide range of buildout requirements and offer a high degree of flexibility.
For example, the new Nortel CDMA Metro Cell, as well as providing a platform for upgrades to full 3G, makes use of fiber to connect the digital enclosure to the radio enclosure at distances of up to 200 meters. This cuts signal loss as well as installation costs for various indoor and outdoor configurations, Murashige says. Operators can deploy the high-capacity digital equipment frame of the Metro Cell in conjunction with minicell or Metro radios, which means they won't have to change out digital frames in instances where they have to move from provisioning for low-density to high-density traffic, he adds.
As well as base station components becoming smaller and more modular, another trend contributing to new network flexibility is implementation of the IS-634 open system radio-switch interface. This allows operators to mix and match various types of switches with PCS infrastructure from different vendors.
One of the first players to exploit this option is U.S. company Chase Telecommunications, Inc., a CDMA PCS operator based in Chattanooga, Tennessee. ChaseTel, with C-block (15 MHz) licenses covering 98 per cent of the population of Tennessee and areas of six surrounding states, is using Qualcomm's new QCore 22 base stations in conjunction with the Alcatel 1000 S12 switching center, says chairman and president Anthony Chase. "It's extremely important to have the technical freedom to select top-tier equipment suppliers," he says."
Brian H. |
