Wireless communications has created a generation of users who are entirely dependent on portable devices for personal connectivity. The underlying technologies have matured to a level where portable telephony is ubiquitous, and a very large and exciting market is emerging. Now, what promises to be the transparent convergence of the Internet and wireless is portable Internet access. The enabling technologies of packet radio, adaptive antenna systems and Internet architectures will make access to the rich content of the Internet as pervasive as cellular telephony today.
Conventional mobile wireless networks, such as Global System for Mobile Communications (GSM), Code Division Multiple Access (CDMA) and Time Division Multiple Access (TDMA), are just starting to offer mobile data services to consumers. Meanwhile, use of the Internet has put unprecedented demands on the land-line infrastructure, resulting in massive build-outs of new broadband transport and access networks. The application of innovative wireless technology fueled by the momentum of the Internet will result in a new class of wireless Internet infrastructure that will give millions access to their favorite Internet experiences on the move.
The entire Internet industry has grown, due to the low entry barrier for a vast variety of content and services. But whereas in many markets wired residential consumers have seen bandwidth rise from 9.6 kbits/s to over 1 Mbit/s at affordable prices, the same consumers are barely able to gain access to the Internet when they leave their fixed, wired connections. Although an industry has evolved around "broadband wireless" systems, these are targeted to providing rapid connectivity to locations and buildings, not people.
For years, the mobile wireless industry has been skeptical about wireless data, but there are a few widespread consumer success stories: for example, the numerous applications and end-user devices in the Personal Handiphone and i-Mode networks in Japan, and the enormous adoption of short messaging service in GSM networks. But the adoption of packet-based networks for wireless systems has been gated by the need to provide circuit-switched voice services on these networks. Consequently, the adoption of end-to-end packet networks has been slowed by the lack of consumer demand. And, most end-user devices are based on telephony rather than designed as Internet appliances. Only recently have portable Internet appliances designed for wireless connectivity emerged.
One premise for the lack of success of mobile data was the "not enough bandwidth" theory: Unless wireless can reach massive bandwidths, there will be no killer apps for wireless data. Another is that there really are no such killer apps for wireless data, although this view is changing now that the Internet industry has exploded.
Mobile wireless applications can be categorized into segments that become increasingly more demanding of complexity, bandwidth and transparency to Internet content and protocols. Basic Internet content (e.g., weather, stocks, news) is widely available today in most commercial mobile networks, using the Wireless Application Protocol (WAP) and Web clipping techniques, and is delivered to mobile phones in text form.
Over the next few years, network-enhanced applications-those that require some level of intelligence and transactional capability in the network-such as geolocation-ready applications, will emerge on these devices. Those applications have real value and are not demanding of bandwidth-only of network intelligence and preprogrammed interaction between the network and the user. Next, there is a variety of applications that require some level of security and reliability, such as mobile secure commerce and corporate access to intranets. Here, the issue is more complex in that the end user has some specific and very demanding needs, such as security and encryption; those problems are being solved today.
ArrayComm has developed the i-Burst system architecture to provide business users and consumers with access to the Internet at unprecedented data rates, with freedom to move, and an always-on experience. Essentially, the system attacks both premises for the lack of success of wireless data: offering unprecedented bandwidths and transparent access to all the content of the Internet and any content, public or private, which is based on the Internet Protocol.
The growth of the Internet is the key engine behind i-Burst. The greater the use of the Internet in day-to-day life and the greater the breadth of applications on the Internet, the greater will be the need for a service like i-Burst. What i-Burst offers is the "mobile multimedia experience." The best minds in the world have already started down this path of a virtual mobile experience, whether it's the wearable-computing people at MIT's Media Lab, the students at WinLab working on "infostations," or the "infopad" concepts from Berkeley.
The core technology ArrayComm has developed is adaptive antenna array processing. This is a suite of techniques for improving the spectral efficiency of wireless communications systems.
The signal processing involves both spatial and temporal processing of the radio signals received in a small array of antennas. The signals are processed using complex matrix manipulation in multidimensional mathematical space to mitigate interference in multiple-access wireless networks. Algorithms process the transmitted signals from a user and determine the antenna pattern, which is constructed instantaneously for optimal transmission to that user. This is done concurrently for all the users, using the frequencies in the reach of that antenna location.
Those same techniques allow the adaptive processing to reduce the antenna array gain in the direction of significant interferers, thereby reducing the effects of co-channel interference. This entire process is completed in every frame of the bit pattern-more frequently than every 5 milliseconds-so that the whole radio environment can change significantly, and yet the signal processing can keep up to reconfigure the transmission and reception patterns from tens of users within reach of a basestation.
The radio technology used in the system is based on a Time-Division Duplex protocol. That protocol uses the same frequency for transmission and reception of radio signals, unlike conventional cellular and PCS systems, which use a different frequency for each of those functions. A common assumption about such systems is that they can serve only microcellular coverage (i.e., less than 2 kilometers), but ArrayComm's technology offers cells of over 10 km in radius. A fundamental aspect of this technique-the reciprocity created by using the same frequency for transmission and reception-is that the radio patterns received at the basestation antenna are an accurate signature of the transmitter and the geographic environment, as well as all the interferers and other users in the area. Therefore, this signature is a perfect template by which signals can be shaped to accurately reach their respective destinations, with a high degree of fidelity.
In conventional cellular systems, it is possible to use an estimation of the signature at one frequency such as the basestation-receive frequency, to synthesize the patterns at the other frequency, for example, the basestation-transmit frequency, but since the wavelengths are different and the propagation and fading characteristics are subtly dependent on the wavelength, dead reckoning cannot be used to compensate for those effects.
When adaptive algorithms are used at a basestation, a benefit is derived that accrues immense advantages at the network level. Since the system is adaptive, the power levels and channel characteristics are determined simply by taking a snapshot of the immediate environment.
Within the i-Burst architecture is an open services platform, which supports the delivery of content and applications over the access network from multiple application service providers (ASPs). Combined with the tunneling and subscriber management system, this architecture is aimed at stimulating numerous application vendors and service providers to compete for access to end users, much as vibrant competition has stimulated use of the Internet today.
ArrayComm foresees a new breed of application developers who will extend broadband applications to the portable domain, as well as invent them specifically for that domain, such as broadband geolocation services and content. Such services would include entertainment, tourism, gaming and instructional content.
The range of applications for the I-Burst system is very broad, since the fundamental application is Internet access. Even though the system is for portable access, one application is to serve end users who have fixed locations, such as small office/home office desktop computers, which require high-speed Internet connectivity. End-user devices planned for i-Burst service will all be Internet-enabled appliances. We expect to see laptops, Web pads and personal digital assistants equipped with the architecture embedded. The family of Internet-enabled appliances will also encompass gaming devices and personal entertainment systems. As the protocol is widely deployed, we expect users will have multiple personal devices with i-Burst connectivity, so they can always stay connected.