**2.5. Simulation model**

6 Will-be-set-by-IN-TECH

depends on the choice of the utility function; specifically on its mathematical properties. The most common existence result for a game's NE is given by the Glicksberg-Fan-Debreu fixed

This chapter assumes an autonomous sensor, positioning, and identification network (SPIN) as the example system in all investigations. A SPIN is a system characterized by a medium to high node density (up to 2-3 nodes per *m*2) in industrial factories or warehouses. Nodes transmit low to medium rate data (up to 1Mbps) combined with position information (position accuracy under 1m) over medium to long distances (typically less than 30 m) to

Concretly, we consider a cluster of up to a hundred IR-UWB sensor nodes that transmit data packets to one common receiver, called the cluster head (CH). The network operation model is based on the beacon-enabled mode of the IEEE 802.15.4a standard [8]. Each sensor node (SN) is considered a source; a link is formed by a transmitting node (source) and the cluster head (CH). Users are asynchronous

• **Scenario 1- Continuous transmission**: Up to 10 UWB sensor nodes are equidistantly situated to the CH, but not necessarily to themselves, along a circle of radius 10 m. They

• **Scenario 2- Factory hall**: This scenario accounts for a square simulation field with dimensions 30m×30m. In this field, 100 IR-UWB sensor nodes are considered: 5 are collocated at fixed positions, 75 move along a production line at 5m/s while the rest randomly moves at the same speed within the simulation field. It is assumed that each sensor node generates packets following an exponential distributed packet inter-arrival process and that the exponential processes of the individual sensor nodes are statistically

30m

CH

5 fixed UWB nodes

75 UWB nodes, v=5m/s

(b)

20 mobile UWB nodes, v=5m/s

30m

independent. The maximum information data rate per sensor node is 50 Kbps.

10m

UWB node

**Figure 2.** Investigated scenarios: (a) Continuous transmission vs. (b) Factory hall.

CH

(a)

point theorem [7].

a common receiver.

**2.4. Investigated scenario**

among themselves. We investigate two scenarios:

continuously send packets to the CH.

The dynamic simulation model has been developed with the discrete event simulation system OMNeT++ [15]. The CH and each SN comprise a PHY layer, a DLC layer and an application layer instance; network and transport layer operation is transparent. For the air interface the superframe structure described in Section 5.4.1 of the IEEE 802.15.4a standard [8] has been selected.

At the application layer each SN generates data packets according to an exponential distributed packet inter-arrival process. Packets are addressed to the CH; its size has been chosen to be *Lp* = 400 bits. The exponential processes are statistically independent from each other, and a maximum information data rate of 1 Mbps is considered. The DLC layer implementation corresponds with the basic "data transfer model to a coordinator" in the standard IEEE 802.15.4a [see 8, Section 5.5.2.1]. For each DLC packet a packet error rate (PER) is calculated as a function of the received power, interference from concurrent transmissions and thermal noise. At the MAC layer a link adaptation function has been implemented which aims at optimising link/system capacity under several channel and interference conditions. The development and analysis of this function is the main achievement of the work presented in this chapter and is covered in section 3.

It is assumed that the network has a fixed chip duration, *Tc*, so that all changes at the PHY layer transmission parameters are induced by instructions coming from the MAC/DLC layer. The selected set of PHY layer parameters remains constant for one MAC packet transmission, but can be changed from packet to packet according to the time variant channel and interference conditions.
