Technical Challenges for Broadband Wireless

the technical challenges of developing and deploying a successful broadband
wireless system. The discussion presented in this section sets the stage for the rest of the
book, especially Part II, where the technical foundations of WiMAX are discussed in detail.
To gain widespread success, broadband wireless systems must deliver multimegabit per second
throughput to end users, with robust QoS to support a variety of services, such as voice,
data, and multimedia. Given the remarkable success of the Internet and the large variety of
emerging IP-based applications, it is critical that broadband wireless systems be built to support
these IP-based applications and services efficiently. Fixed broadband systems must, ideally,
deliver these services to indoor locations, using subscriber stations that can be easily selfinstalled
by the enduser. Mobile broadband systems must deliver broadband applications to laptops
and handheld devices while moving at high speeds. Customers now demand that all this be
done without sacrificing quality, reliability, or security. For WiMAX to be successful, it must
deliver significantly better performance than current alternatives, such as 3G and Wi-Fi. This is
indeed a high bar.
Meeting these stringent service requirements while being saddled with a number of constraints
imposed by wireless make the system design of broadband wireless a formidable technical
challenge. Some of the key technical design challenges are
• Developing reliable transmission and reception schemes to push broadband data through a
hostile wireless channel
• Achieving high spectral efficiency and coverage in order to deliver broadband services to a
large number of users, using limited available spectrum
• Supporting and efficiently multiplexing services with a variety of QoS (throughput, delay,
etc.) requirements
• Supporting mobility through seamless handover and roaming
• Achieving low power consumption to support handheld battery-operated devices
• Providing robust security
• Adapting IP-based protocols and architecture for the wireless environment to achieve
lower cost and convergence with wired networks
As is often the case in engineering, solutions that effectively overcome one challenge may
aggravate another. Design trade-offs have to be made to find the right balance among competing
requirements—for example, coverage and capacity. Advances in computing power, hardware
miniaturization, and signal-processing algorithms, however, enable increasingly favorable tradeoffs,
albeit within the fundamental bounds imposed by laws of physics and information theory.
Despite these advances, researchers continue to be challenged as wireless consumers demand
even greater performance.