Network Technologies

UMTS/HSDPA/HSUPA/HSPA

• Performance
• Applications
• GPRS/EDGE Applications on UMTS/HSPA
• IP Address Management

UMTS/HSDPA provides voice service and enhanced data capability at broadband speeds with low latency. UMTS/HSDPA uses the same fundamental architecture for voice and data services as GSM/GPRS/EDGE and can support GSM, GPRS, EDGE, UMTS, and HSDPA. Multi-mode devices can work with both GSM and UMTS/HSDPA.

UMTS is divided into the UMTS Terrestrial Radio Access Network (UTRAN) and the UMTS core network. Operators can use the same core network (consisting of the mobile switching centers and packet data nodes) for both the GSM/GPRS/EDGE radio access network and the UTRAN.

UMTS/HSDPA uses a radio channel called Wideband CDMA (WCDMA) which provides high speed data channels (with devices supporting peak rates of 7.2 Mbps) as well as flexible real-time allocation of resources between voice and data. Compared to GSM, WCDMA is spectrally more efficient, has greater flexibility and control over the type of data communicated, and provides users simultaneous voice and data operation. The WCDMA radio channel can adjust the allocation of code space every 2 milliseconds, allowing the network to dynamically assign the amount of radio resource for different users.

With High Speed Uplink Packet Access (HSUPA), uplink speeds are notably faster as well. The combination of HSDPA and HSUPA is called HSPA.

Performance

HSDPA is the highest-performance cellular-data technology ever deployed. Its peak theoretical rate in 14.4 Mbps. AT&T has engineered its network so that most users experience typical downlink throughput rates of 700  kbps to 1.7 Mbps, with bursts over 1 Mbps. Typical uplink rates are 500 kbps to 1.2 Mbps.

These throughput rates are about five times as high as EDGE and ten times as high as GPRS. (Note that actual user throughputs depend on many factors, including signal quality and network loading.)

Current HSDPA devices commonly support peak rates of 3.6 or 7.2 Mbps, though typical user rates are lower than this.

When operating on a UMTS network that does not support HSDPA, peak speeds are 384 kbps with typical throughput speeds of 220 to 320 kbps.

Not only does UMTS/HSPA have higher data transfer rates, but it also has lower latency. For some applications, latency is as important as data throughput, particularly for time-sensitive applications such as interactive and streaming multimedia and Web browsing of complex pages with multiple objects, as well as for applications such as database transactions that send a lot of packets back and forth. The latency of UMTS/HSPA, as measured by round trip time from the mobile station to a node immediately external to the UMTS network, is 100 to 200 milliseconds. In comparison, GPRS/EDGE latency is about 600 milliseconds.

Applications

UMTS/HSPA supports the same applications as GSM/GPRS and EDGE, including e-mail, group collaboration, Web access, and messaging. However, the higher throughput rates of UMTS/HSPA enable transfer of larger files as well as quicker response time for network applications. UMTS/HSPA throughput is much higher than most modem connections. Any application that works well over a modem will work even better over a UMTS/HSPA connection. UMTS/HSPA devices are well-suited to the following types of applications:

Consumer-focused Applications 

• E-mail with large attachments
• General-purpose Web browsing
• Multimedia (video/audio streaming and downloading)
• Picture and video messaging
• WAP-based applications with rich content

Business/Enterprise-focused Applications 

• E-mail with large attachments
• Virtual private networking
• Complex database transactions
• Intranet access to enterprise applications
• Web-based enterprise applications including enterprise resource planning, customer relationship management and sales force automation

GPRS/EDGE Applications on UMTS/HSPA

Any application suitable for the AT&T GPRS/EDGE network will function well on the UMTS/HSDPA network, especially since UMTS/HSDPA provides higher than average throughputs and lower latency.

Keep in mind that devices fall back to EDGE networking when outside when there is no UMTS/HSDPA coverage, and application performance will vary depending on which network is available. If a user is mobile, the UMTS/HSDPA connection will automatically transfer to EDGE if the user moves out of the UMTS/HSDPA coverage area. The moving device will maintain the same IP address in the transfer; however, there may be a delay on the order of tens of seconds to execute the handover, which may affect any application if in the middle of transferring data.

IP Address Management

IP addresses can either be private or public. With private IP addresses, the network performs network address translation (NAT) between the private IP address assigned to the mobile station and a public IP address used for external communications. With public IP addresses, there is no address translation.

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