Next Generation Wireless Networks
By John C. Colwell, Bishop & Associates Inc.

The introduction of second generation wireless in the mid-‘90s represented not only a major advance from analog to digital voice, but it also set the stage for subsequent developments in the late ‘90s, including Enhanced Data rates for Global Evolution (EDGE), General Packet Radio Service (GPRS), and Code Division Multiple Access (CDMA)—Interim standard (IS-95B). 

Collectively, these data-supporting enhancements are referred to as 2.5G or 2G+ networks. They offered downstream data rates ranging from 64 to 200 Kb/s; suitable for small text messaging and Internet email access, but not much more. Still lacking was the broadband connectivity experience. 2.5G marked the beginning of the shift from circuit-switched to packed-switched data access.

In the post-Y2000 timeframe, wireless network upgrades slowed to a near crawl. However, the standards development organization, known as the Third Generation Partnership Project (3GPP), continued its efforts leading to the deployment of the International Telecommunications Union’s IMT-2000 vision of a global family of third-generation (3G) mobile communication networks. This version of 3G is a Wideband, Code Division Multiple Access (W-CDMA) technology developed primarily by Europe’s GSM community; UMTS is synonymous with W-CDMA in Europe. Universal Mobile Telecommunications System (UMTS) is part of the International Telecommunications Union’s (ITU) IMT-2000 vision of a global family of third-generation (3G) mobile communications systems. UMTS is the 3G technology of choice for GSM networks worldwide.

Time Division Synchronous CDMA (TD-SCDMA) is a 3G network technology that was jointly developed by Siemens and the China Academy of Telecommunications Technology. TD-SCDMA supports synchronous services such as voice and video, as well as asynchronous data services, including Internet access.

Working in parallel with the 3GPP standardization effort is the 3GPP2, or Project 2 organization. Project 2 addresses the technical evolution of CDMA (IS-95) derivative wireless networks. 1xRTT 1X Radio Transmission Technology was the first step in what is referred to as the CDMA 2000 series of standards development. 1xRTT 1X doubled the number of voice channels and increased data rates to a maximum of 153 Kbps.

1xEV-DV 1X (Evolution Data and Voice) is a CDMA 2000-based, 3G mobile network standard providing data rates of 1.2 Mbps for mobile users, with peak data rates up to 5.2 Mbps for stationary users. 1xEV-DV 1X was surpassed by 1xEV-DO technology, which offered improved data performance. 1xEV-DO 1x (Evolution Data Only) is a 3G mobile standard that is the next evolution of cdma2000 (1xRTT). It increased packet data transmission capabilities for mobile phones, but lacked backward compatibility with 1xRTT.

High Speed Downlink Packet Access (HSDPA) is a 3.5G, broadband packet-based data service in a W-CDMA downlink, and the first standard to deploy MIMO (Multiple Input, Multiple Output antennas) and adaptive modulation technologies that enable effective data rates of 10 Mbps. The High Speed Uplink Packet Access (HSUPA) is the corresponding 3GPP uplink protocol that enables the mobile device uplink to operate at data rates up to nearly 6 Mbps. HSPDA and HSUPA mark the beginning of true broadband experience in the cellular wireless environment.     The iPhone, and similar multimedia devices, utilize HSPDA networks. Beyond HSPDA is LTE, or long-term evolution, a 4G network that employs orthogonal frequency division multiplexing (OFDM) and the multiple input/multiple output (MIMO) antenna technology. Architecturally, LTE is leaner and flatter than previous wireless network architectures. LTE is a packet-only, all IP-based network architecture.    

3xEV-DO/DV 3X (Evolution Data Only/Data and Voice) is a standard under development and part of the next generation of wireless network technologies in the CDMA 2000 lineage. It will be an all IP network infrastructure combined with the latest air link technologies, including OFDM and MIMO. OFDM splits the information into multiple narrowband subcarriers, allowing each of them to carry a portion of the information at a lower bit rate. OFDM improves transmission efficiency particularly in urban areas. MIMO utilizes multiple transmit and receive antennas, creating multiple spatial paths on the air interface between the network and the subscriber. The multiple paths carry the same or different streams of information, allowing an increase in either the coverage, due to higher signal to noise ratio (SNR) at the receiver, or higher data throughput.

Other developments include base stations capable of supporting multiple air protocols and the ability to serve multiple carriers.    

 A competing technology for the 4G wireless space is WiMax, which is based on the efforts of the WiMax Forum and the IEEE 802.16 Working Group for Wireless Access Standards. WiMax has been described by Nortel Networks as a profoundly disruptive technology. Potentially, it turns the economic paradigm of cellular telephony upside down, while at the same time creating a whole new competitive environment. Today, wireless carriers subsidize handset ownership and control the services available to the subscriber. Their revenues are based on minutes of use and charges for those services they choose to offer. In a WiMax environment, a subscriber equipped with a dual-mode phone, or a WiMax-enabled PC, has the options of accessing either the Internet through any service provider or through the traditional wireless carrier. This opens the barn door for a wide range of services, including location-based information services that will drive advertising-based revenues. We do not know exactly how this will all play out, but we do know that change is in the offing and it will be exciting.

From the packaging and interconnection standpoint, WiMax has approximately one-fifth the complexity of a typical cellular base station. The radio is generally built directly into the antenna assembly. (See below, left.)

The equipment cabinet typically contains basic, off-the-shelf switching and routing equipment for those carriers that want to “roll their own.” Integrated solutions are also available from suppliers such as Axxcelera Corp. and others. (See above, right.) The connections between the equipment cabinet and the antenna are comparatively simple, consisting of a copper or fiber-based signal connection and a power connection.

The customer premises equipment is shown at the left. The form factor is similar to a wireless cable modem.

Some of the key supporters of WiMax are Intel, Motorola, Nortel, Alcatel-Lucent, Ericsson, and many others. A complete list of supporters is available from the WiMax Forum.

John Colwell Director, Telecom, Medical and Instrumentation, Bishop & Associates Inc. John Colwell’s background includes 10 years at Nortel Networks‑Cable Group, where he directed the U.S. premises cable marketing effort. In addition, Colwell directed Nortel's global product development group. Prior to joining Nortel, Colwell held positions in engineering, business planning and development at Amphenol Corporation.