Digital Signal Processing Reference
In-Depth Information
Fig. 5.1
IEEE 802.11 and IEEE 802.15.4 both operate in the 2.4 GHz ISM band. This leads to
coexistence issues, most prominently at the side of the ZigBee network
selection to the observed interference patterns. Importantly, the algorithms are eval-
uated for coexistence with IEEE 802.11 systems. However, they are designed to be
so flexible that they can adapt to any interference pattern, as long as the coherence
time of the interference is longer than one IEEE 802.15.4 period.
This chapter is structured as follows. First, we explain the system model in
Sect.
5.2
. The benchmark solution for this chapter is presented in Sect.
5.3
.In
Sect.
5.4
, we describe the problem statement and how we can reformulate the prob-
lem for practical use. We also detail the downsides to the problem reformulation.
In Sect.
5.6
, we design learning-based algorithms, that eliminate the scanning over-
head. In Sect.
5.7
, we show that these energy-efficient learning-based algorithms
outperform the scanning-based approaches. Finally, in Sect.
5.8
, we present out con-
cluding remarks.
5.2 Modeling Coexistence
In this section we give a short overview of the models used for the sensor network,
the WLAN interference, and the considered energy and performance metrics that
are relevant for the considered scenario. For a more detailed overview of the as-
sumptions made and the implementation details, we refer to [19, 65].
5.2.1 IEEE 802.15.4 Network Model
Sensor networks typically consist of a large number of terminals, e.g., to monitor the
environment or for building automation. As a result, we represent the IEEE 802.15.4
network by a large number of terminals
n
that are arranged in a string. The con-
nectivity matrix
C
(n,n)
denotes which sensors can overhear which others. We as-
sume that all sensors in the range
Rd
can overhear each other's beacons, where
d
is the inter-terminal distance. In Fig.
5.2
a simple string topology is presented with
