SDR Baseband Requirements and Directions to Solutions
This chapter puts the development of SDR baseband technology into functional and historical perspective, then examines the evolving spectrum of requirements from mobile devices such as simple handsets, through complex mobile devices, access points, micro cellular basestations to wide area basestations. Both internal functional requirements and external interface requirements are considered. The requirement challenges are then discussed in the context of currently available (and emerging) technologies for implementing SDR baseband processing subsystems. The chapter concludes with a consideration of likely successful implementation directions.
1.1. Baseband Technology and the Emergence of SDR
The primary intent of SDR is to allow a wireless device to change functionality by switching in different software stacks (or software-like objects) that can be stored locally or downloaded over the air .
1.1.1. Wireless Architectures
At the highest level, all wireless systems can be decomposed into four subsystems (see Figure 1.1). The baseband subsystem sits between the RF front-end and the controller. It is responsible for end-user data encoding/decoding and signal modulation/demodulation. The encoding/decoding function can be classified as a low speed signal-processing task and the modulation/demodulation task can be classified as a high speed signal-processing task.
By the end of the Second World War, wireless ...