Wireless Network Design: Optimization Models and Solution ...

4 Jeff Kennington, Eli Olinick, and Dinesh Rajan
the location of these BTS and APs is the primary focus of Chapters 5 and 6. While
these two problems appear to be similar, there are several crucial differences: i) the
quality of service requirements depends on the specific applications supported by
the networks and may be different in the cellular and WLAN cases, ii) the signal
propagation in indoor and outdoor channels is very different which requires the use
of different models, and iii) constraints used in formulating the optimization problem
are different in the two cases. For instance, the cost of a BTS is significantly
higher than the cost of APs, and is a primary concern for cellular operators 1 . The
primary focus of Chapter 5 is the design of 3G cellular networks based on CDMA
technology. The primary focus of Chapter 6 is the design of 802.11 based WLANs.
One common and critical ingredient in all wireless networks is the requirement
for radio frequency (RF) spectrum. Networks can be classified into two types based
on the spectrum being used: licensed and unlicensed networks. The use of a licensed
spectrum is regulated in each country by an agency such as the federal communications
commission (FCC) in the United States. Examples of networks using licensed
spectrum include the cellular networks at 1800 and 1900 MHz. Similarly, networks
that use unlicensed spectrum include the 802.11 based WLANs and Bluetooth networks
that operate in the 2.4GHz industrial, scientific, medical (ISM) band. The advantage
of using the unlicensed band is that the spectrum is free to use. However, interference
from other devices which use the same frequency band can cause disruptions
in wireless service. While the use of the licensed spectrum is more controlled,
obtaining a license to operate a device in a licensed spectrum can be expensive. In
most countries, spectrum is allocated to various operators via an auction process.
Chapter 7 gives a history of spectrum allocation with a focus on the Simultaneous
Ascending Auction (SAA). In the past, agencies such as the FCC have raised billions
of dollars in revenue by selling spectrum in SAAs. A potential risk to wireless
service providers bidding for spectrum in an SAA is that they might win only part
of what they require for a particular network design and overpay for the resulting
“sub-package” of their desired frequencies. Chapter 7 discusses newer designs that
eliminate this risk by allowing bids on “all or nothing” packages of licenses. An
understanding of the formal optimization framework described in Chapter 7 for the
design of spectrum auctions can help operators plan their strategy for obtaining this
crucial resource.
Chapter 8 discusses the importance of designing cellular networks with increased
reliability. Specifically, redundancy is built into the cellular backbone network to
overcome connectivity problems arising out of node and link failures. Several flavors
of this problem and solution methodologies are addressed in this chapter.
Chapters 9, 10, and 11 are focused on the area of optimizing the performance
of ad-hoc wireless networks. A mobile ad-hoc network (sometimes referred to as
MANET) is a collection of nodes that communicate with each other using a multihop
forwarding mechanism without any backbone network support. One of the
primary challenges in a MANET is the node routing problem, where each node tries
to establish a route to send packets to its intended destination. Numerous routing
1 The emergence of inexpensive pico base stations is beginning to create a new dimension to
consider for cellular operators.