2 1 Introduction
Besides, it is unlikely that a user will enable all of these standards at the same time
in a single terminal. Thus, there is a need for a flexible hardware platform capable of
supporting operations among multiple standards and tasks and allocating resources
dynamically to suffice current computational demands.
In addition to the multi-standard multi-task support, flexibility is required to cope
with the rapid evolution of baseband processing algorithms and enable run-time
algorithm adaption to provide better Quality of service (QoS) and maintain robust,
reliable, and seamless connectivity. Furthermore, benefiting from the hardware
reconfigurability, such architectures have the potential to perform system updates
and bug-fixes while the system is in operation. This feature will prolong product
life-time and ensure benefits in terms of time-to-market [13, 15, 16]. Last but not
the least, from an algorithm development perspective, reconfigurable computing
provides a more software-centric programming approach. This allows hardware
platforms to be developed on-demand and potentially in the same language as
used for software development. Unified programming environment enhances pro-
ductivity by simplifying system integration and verification. Besides its importance,
the target subject faces many design challenges in practical implementations, such
as requirements of high computational performance and low energy consumption.
Primary concerns for contemporary system designs are shifting from computational
performance to energy efficiency [2, 17]. This trend becomes more and more
prominent in wireless communication designs. For example, the transition from 3G
to 4G wireless communication systems demands 3 orders of magnitude increase in
computational complexity, whereas the total power budget remains approximately
constant in a single mobile terminal [14, 21]. Reconfigurable architectures, since its
invention in 1960 [10], promise to offer great hardware flexibility and computational
performance. They allow run-time hardware reconfigurations to accelerate arbitrary
algorithms, and thus extend the application domain and versatility of the device.
However, due to huge routing overhead, they cannot match power and area effi-
ciency of ASICs, in spite of their tremendous developments over the past decades.
As an example, fine-grained interconnects in commercial Field-programmable gate
array (FPGA) consume over 75 % of the chip area [20], and cause 17–54 times
area overhead and 5.7–62 times more power consumption in comparison to ASICs
[12]. Moreover, bit-level function blocks of FPGAs incur additional area and
power penalties when implementing word-level computations. The area and power
overhead have restricted the usage of reconfigurable architectures in cost-sensitive
applications such as wireless communication in mobile terminals. To address these
overhead issues, new types of reconfigurable architectures with coarse-grained
function blocks have gained increasing attention in recent years in both academia
and industry [1, 4, 6, 11, 18, 19].
This book presents a coarse-grained dynamically reconfigurable cell array
architecture, which is designed and tailored with a primary focus on digital
baseband processing in wireless communication. By exploiting the computational
characteristics of the target application domain, the presented domain-specific cell
array architecture bridges the gap between ASICs and conventional reconfigurable
platforms. The flexibility, performance, and hardware efficiency of the cell array are
demonstrated through case studies.