THE NINETIES WAS THE DECADE IN WHICH mobile telephony became ubiquitous. The goal was simple—just let people make telephone calls anytime, anywhere. The current decade is going to be the one in which this feat is replicated for data access anywhere, and in a more limited fashion for multimedia access as well. But this is going to be vastly more complicated, fragmented, and interesting. The business models are not clear, the technologies are rapidly changing, and the variety of devices, applications, and user needs are all over the map. One thing is clear—the model is moving from a centralized (think FCC and large carriers) planned scenario to a more laissez faire, adaptive set of offerings. Therein lies the risk, but also the opportunity.

Standards
A significant trend in wireless which has recently accelerated is the proliferation of standards and technologies. Part of the reason is that there are a number of conflicting requirements depending on whether the applications need low or high bandwidths, whether the traffic is bursty or streaming, and whether the network dimensions are on the order of miles, or hundreds or tens of feet.The large num-ber of standards leads to interoperability issues which could hamper the growth of the networks.

Or so one would think. The flip side is that multiple standards enable a variety of opportunities, leading to a constant evolution of systems, tech-nologies, and app-lications. The ideal situation (leaving cost and management issues aside) would be one in which each device and each application could pick and choose the transmission scheme, protocol, and frequency band which would uniquely suit its needs at the moment. While seemingly far-fetched, it is in fact the point towards which networks, systems, and devices seem to be converging.

Multimode/Multiband Radios
These are already commonplace in cellular telephones, most of which can operate in analog mode as well as in one or more digital modes, and in multiple cellular bands. The coming year is going to see the adoption of multimode/multiband radios in wireless local area data networks, with 802.11 a/b/g systems becoming the default. Cellular phones will also begin to have wireless LAN chipsets embedded in them, and PDAs will have both WAN (Wide Area Networking) and wireless LAN modules to enable indoor and outdoor connectivity. The market will drive towards cost-effective power-efficient single chip solutions that incorporate several WAN and LAN standards.

Software-Defined Radios
A subset of these multimode radios is known as Software-Defined Radios (SDR). These reconfigurable radios can be “reprogrammed” on the fly to receive and transmit according to a variety of protocols, standards, and frequency bands. The advantage of these radios is not only to adapt to various transmission techniques, but also to keep up with evolving standards. There is typically a cost penalty associated with this approach, so they will be initially deployed in base stations and other relatively cost-insensitive equipment.

Hotspots and WAN/LAN Integration
Mobility is the primary reason for the existence of most wireless networks. Cellular networks deal with mobility by providing roaming facilities with handoff, and things work relatively seamlessly. Due to the proliferation of bands, both licensed and unlicensed, and the various wireless technologies and standards, there is a need for managing connectivity and session persistence when traversing heterogeneous networks. The most immediate example is that of WAN/LAN integration, enabling users to be connected at high speeds when indoors and dropping to a lower speed wide-area network when outdoors. A number of carriers, large vendors, and startups are pursuing opportunities in this area. Business models and pricing plans are still tentative, and deployments will take a while to become widespread, thereby increasing the utility of these services.

While this will take several years to become widespread, early deployments have already sprung up, and more are to be expected in the coming year.

Spectrum
The basis on which all wireless systems are built is spectrum. The problem is that if it's licensed spectrum it's usually expensive (and scarce). If it's unlicensed then it's noisy and unreliable (and scarce). In the rare event that it isn't scarce today, it is going to get that way before long since user data throughput requirements always expand to fill the bandwidth available to them. Most innovations in wireless have been motivated by a desire to use spectrum more efficiently. The move from analog to digital, the claims of CDMA over TDMA, multiple antenna techniques, etc. are all examples of this, driven by the high prices of cellular spectrum. To get a sense of the size of these numbers, the 1994 PCS spectrum auction for 48 regions netted the government over $7 billion. With sanity returning to the spectrum auctioning process, the numbers have become more reasonable of late. But it is clear to all operators that they need to utilize this expensive real estate very effectively.

Smart, Adaptive Radios
In the cellular world, the ability to squeeze more bits (i.e., calls or users) in a slice of frequency translates directly into more revenue. In the unlicensed world of wireless LANs and PANs (Personal Area Networks), the ability of radios to react to interference and jump to benign frequency channels will affect the performance and capacity of the wireless networks. Management and control systems to dynamically optimize frequency allocation will work in conjunction with adaptive radios to enable self-configuring networks. Rudimentary systems to do some sort of dynamic resource allocation already exist; these will quickly become more sophisticated.

Space-Time Processing and Multi-Antenna Systems
Advances in communication systems relating to data rate, coverage, and capacity have traditionally depended on better use of bandwidth, power, and modulation schemes. One untapped dimension that has recently shown to have the greatest promise is that of space—the use of spatially separated signals to simultaneously achieve substantially higher data rates, capacity, and coverage, in addition to performing robustly in the presence of interference. Initial systems using space-time processing have been announced for wireless WANs, LANs, and fixed wireless systems. Activity in this area is picking up, and this will be a fertile area for growth in the coming years.

Mesh and Ad-Hoc Networks
Another set of self-configuring networks seeks to solve coverage and backhaul problems by deploying mesh networks. In this approach the base stations pass user data to each other in a relay fashion so that only a small fraction of them need to be wired. In ad-hoc networks this concept is taken one step further, with subscriber equipment communicating directly with each other and relaying data to base stations, thereby reducing the need for base station coverage.

Short-Range Communication
The introduction of Bluetooth has allowed cables to be replaced by wireless connections. It is expected that prices will drop to the point where this could become widespread. Two drawbacks of Bluetooth are the susceptibility to interference (from 802.11 devices as well as microwave ovens and other unintentional transmitters in the band) and the low data rate of the Bluetooth radios. For higher speed connections Ultra Wideband systems are beginning to emerge. The FCC's allocation of spectrum for UWB transmission earlier this year has spurred activity in this area. The data rates will be competitive with Firewire and USB 2.0, in the range of several hundred megabits per second. The standards activity has begun in the IEEE 802.15.3 group, and this should give further impetus to the efforts. This is a potentially large opportunity and represents the next generation of high-speed wireless connectivity.

What's Next?
In the next few years the adoption of new technologies and applications is going to be most rapid in the home, with home networking and consumer electronics driving most of this. Enterprises will be the most profitable, but also the least innovative market segment. Here we will see consolidation and rapid growth of wireless networks, but the focus will be on scaleable, manageable, and secure systems. The carrier market will be the most volatile, with many trial balloons being floated, including wireless wide area data, high-speed hotspots, location-based services, a smorgasbord of pricing plans, and so on. A wide variety of technologies and systems will swallow huge amounts of investment dollars, a smaller number will actually be offered to the public, and a tiny fraction will survive. The opportunities are immense and the game is afoot.