Digital Signal Processing Reference
In-Depth Information
handsets have started supporting multiple modes over the past years. Initially, this
has been achieved by integrating multiple radios into one handset. However, when
the number of radios increases, the cost, size, and weight of the terminal are also
affected. Hence, a single radio that comprises all necessary functionality is highly
sought-after [1, 2]. Users want to enjoy a multitude of services on one terminal. Pre-
dictions claim that handheld devices need to support at least six different radios at
the short term. Hence, also from a functionality point of view, flexibility is becoming
essential.
1.2.1.2 Enabling Seamless Connectivity
Ubiquitous and seamless connectivity can be achieved in a heterogeneous network
environment, under the condition that both terminals and network feature the neces-
sary reconfiguration capabilities to support horizontal (between access points of one
technology) and vertical (between access points supporting different technologies)
roaming. Recently, the need for such reconfiguration support is receiving attention
in specific standardization initiatives (see Chap. 2).
1.2.1.3 Scaling Technology Imposes Reconfigurability
Gordon E. Moore predicted 45 years ago, that the number of transistors on a chip
would double about every 2 years. So far, history has proved him correct [3]. Scal-
ing has brought enormous processing capabilities packed on small areas, opening
opportunities to implement flexible platforms at low cost and low power.
However, for newer technologies, the Non-Recurring Engineering (NRE) costs
related to System-on-Chip (SoC) design are rising exponentially. On top of this,
design cost has increased dramatically and is expected to continue to do so. Not only
is the design complexity increasing, CMOS scaling has arrived at the point where
parasitic problems are becoming dominant. As these effects cannot be resolved at
the transistor side, new designs will need to take these problems into account.
The question whether scaling is still viable is sounding louder each day, espe-
cially for custom ASIC chips. While higher production volumes can still compen-
sate the NRE costs, cost trade-offs show, already today, an advantage in using re-
configurable radios to single-mode devices for smaller markets. For these instances,
the extra area penalty is not significant compared to the cost cutting in NRE.
The extra area penalty can be furthermore easily compensated for multi-mode
terminals. In those terminals the possibility exists to reuse silicon and thus signif-
icantly reduce overall area, which makes flexible platforms even more attractive.
Also other cost factors, like assembly cost, form factor and time-to-market, direct
towards chip reuse and, hence, the HW platform paradigm [4, 5].
