2. Wireless Personal Area Network (WPAN)
Short range wireless (SRW) communications is expected to play an important role in the wireless
networks.
A PAN using wireless network technologies is known as the Wireless Personal Area Network.
A WPAN is a personal, short distance area wireless network for interconnecting devices centered
around an individuals workspace.
WPANs address wireless networking of mobile computing devices such as PCs, peripherals, cell
phones, etc….
WPANs are also called as the “short wireless distance networks”.
Replacement of cables.
3. WPAN typically extend to 33ft or 10m or less.
Due to its low range it is used mainly as a replacement to cables.
Used in wide range of retail and industrial applications.
Major technologies of WPAN are Bluetooth (802.15.1) and Zigbee (802.15.4).
4. Network Architecture
WPAN architecture consists of master and slave configuration.
The slave devices and high end user interface master devices communicate over an network with
the data rate of alteast 10Mbps.
The low end user interface devices behave as slave devices of a master device with the
communication requirement below 1Mbps.
All the communication devices have radio that aids in communication.
Figure 1: WPAN architecture
5. The Figure 1 shows the WPAN architecture with the master devices (desktop or laptop), and
Slave Devices as mobile phone, printer, scanner etc.
Master controls the transmission schedule of all devices in WPAN.
Slave can communicate with the master and can communicate when granted permission by the
master.
The master gives its clock and device ID to all slaves in its piconet.
Two connnectivity topologies are defined in the WPAN:
The piconet and scatternet.
6. Piconet
A piconet is a WPAN formed by a device serving as a master and one or more devices serving as slaves in the network
as shown in Figure 1.
As the enabled device comes within the range, master is selected by establishing the connection with the other devices
setting the frequency hopping sequence and system clock to determine the phase.
At any time the data is transferred between the master and any one slave.
The master switches rapidly from slave to slave in a round robin fashion.
7. Any device may switch the master slave role at any time.
Slaves communicate only with their master in point to point fashion under the masters
control.
The masters transmission can be either point to point or point to multi point.
Besides in an active mode the slave device can be in standby mode to reduce power
consumption.
8. Scatternet
A scatternet is a collection of operational piconets overlapping in time and space.
A device that is a member of two or more piconets is said to be involved in scatternet.
9. Here two piconets are connected through a common slave.
A device may participate in the several piconets at the same time.
Thus allows the possibility that information flows beyond the coverage area of single
piconet.
A device in a scatternet could be a slave in several piconets but master in only one of
them.
The performance of a WPAN highly depends on the scatternet structure.
10. WPAN Components
WPAN components range from very low power devices with low power operation.
Also to a high end devices covering the full range of communication standards.
Low rate devices ex: sensors (data in bps) whreas high rate devices like 10 Mbps.
11. Requirements of WPAN devices
Device in a WPAN must be of low cost.
The device must operate for a long time from simple battery.
Because of large number, they must be small such that user is hardly aware of their
presence.
The devices are small in size.
Ease of use.
12.
13. WPAN Technologies and Protocols
The IEEE 802.15 is the IEEE working group established in January 1999 to develop
standards for WPAN.
The IEEE 802.15.1 (Bluetooth) has been proposed as cable replacement technology
for wireless personal devices.
IEEE 802.15.2 describes the coexistence of WPANs with other wireless devices in
unlicensed frequency band.
The IEEE 802.15.3 standard have been proposed for high rate (HR WPAN
applications).
The IEEE 802.15.4 standard (zigbee) has been drafted for low rate WPAN (LR-
WPAN) applications.
IEEE 802.15.5 for mesh based WPAN.
14. Bluetooth (IEEE 802.15.1)
IEEE 802.15.1 is a WPAN standard based on Bluetooth v1.1 specifications.
Which is a short range radio technology operating in the unlicensed 2.4Ghz frequency
band.
The main goal of Bluetooth was to replace cables.
But now this technology is also used to interconnect various Bluetooth devices and
facilitate more ways of exchanging data.
The protocol stack arrangement of Bluetooth is shown in Figure 4.5.
16. Physical radio layer (radio frequency, RF) receives and transmits voice and data.
Baseband layer enables physical RF link between Bluetooth units that forms a piconet.
Link manager is the protocol that handles link establishment between Bluetooth devices which include
authentication and eccryption.
Logical Link Control and Adaptation Protocol (L2CAP) is a lower connection based Bluetooth
communication protocol that implemets multiplexing.
17. The audio profile is responsible for managing connections for
sending/receiving controls to/from audio devices.
They are used to control encoding/decoding audio data and sending/receiving
it to/from headset.
The control block processes various control operations for connectivity
management of devices.
Other logic link control (LLC) profiles that are optional in devices are cordless
telephony, headset etc.., file transfer and synchronization.
Radio Frequency Communication (RFComm). Multiplexing and flow control are
implemented here.
18. Telephone Control Specifications (TCS) is a bit oriented protocol that defines the call control
signalling for establishment of speech and data calls between Bluetooth devices.
Service Discovery Protocol (SDP) is a Bluetooth service discovery protocol that handles publishing and
discovery of services running on the top of the Bluetooth stack.
Application profile supports audio applications, network applications, telephone service applications
and management applications.
19. Bluetooth opertions can be summarised as:
1. A radio (RF) that transmits and receives data and voice.
1. A baseband or link control unit that processes the transmitted or received data.
1. Link management software that manages transmissions.
1. Support application software.
20. Bluetooth radio is a short distance radio that operates in the unlicensed spectrum of 2.4 Ghz.
Its nominal antenna uses the power of 0dBm.
For 0dBm the range is 10m.
Data are transmitted at a maximum rate of 1Mbps.
21. PHY Layer
The baseband is the PHY layer of the Bluetooth.
Baseband is the hardware that turns the received radio signal into digital form
which can be processed by the host application.
The baseband processor handles all the tasks that are performed on the
packets.
22. Each packet contains the information about where it is coming from, what
frequency it is using, where it is going.
Base band functions as a link controller.
13 different packets are defined for the baseband layer of the Bluetooth
system.
SCO, ACL
Synchronous Connection Oriented link, Asynchronous Connection link
SCO:voice
ACL:packet data
13 different packets
23. ID: 68 bit packet, used in paging, inquiry and response routine.
NULL: 126 bit packet, consists of channel access code, packet header.
POLL: It requires confirmation from the destination.
Frequency hopping Synchronization: 144 infobits and 16 bit CRC (cyclic redundancy check) code.
Data medium rate 1 (DM1): carries information data only, 16 bit CRC code and 18 infobytes it contains.
Data high rate 1(DH1): It carries 28 infobytes and covers a single time slot.
AUX1: Resmbles DH1 packet except that it has no CRC code and carry upto 30 infobytes.
DM3: 3 time slots it covers and can carry 123 infobytes.
24. DH3: 3 time slots it covers and can carry 185 infobytes.
DM5: 5 time slots it covers and can carry 226 infobytes.
DH5: 5 time slots it covers and can carry 341 infobytes .
HV1: High quality voice 1 carries 10 infobytes.
HV2: carry 20 infobytes.
HV3: carry 30 infobytes.
Data voice (DV): It consists of fixed voice field of 80 bits and a data field of
150 bits.
25. Link layer
The LM software runs on the microprocessor, and manages the communication between the
Bluetooth devices.
Each Bluetooth device has its own LM ( Link Manager ).
When one of the devices discovers other remote link managers protocols (LMP) to handle link
set up, authenticate Qos, encrypt and adjust data rate on link.
To perform service provider role the LM uses the service of the underlying Link Controler (LC).
The LC is a supervisory function that handles all Bluetooth base band functions and supports
link manager.
26. It is responsible for following functions:
1. To send and receive data. Able to identify sending device and perform
authentication.
2. It determines what type of frame to be used in slot by slot basis.
3. It directs how devices will listen for transmissions from the other devices or
put the devices in various power save modes.
Each packet uses a single 625 usec but can extend upto 5 slots.
27. Application software
The last basic part of Bluetooth system is application software.
The application software is set in a device that operates an application over the Bluetooth
protocol stack.
This software allows the mobile phones to do its job.
HCI (Host Controller Interface) provides a command interface to baseband controller and
link manager.
28. It access the hardware status, control registers it provides a uniform method
of accessing Bluetooth baseband capabilities.
HCI is functionally broken into 3 separate parts.
HCI firmware, HCI driver, Host controller transport layer.
29.
30.
31.
32.
33. IEEE 802.15.2 (Coexistence)
The IEEE 802.15.2 is concerned with the coexistence issues that arise when two wireless systems share
an environment of operation.
It has two goals: to quantify the effects of mutual interference between WPAN and WLAN devices.
To establish mechanisms for coexistence of WPAN and WLAN (eg: IEEE 802.15.1 and IEEE 802.11b) at
both MAC and PHY layers.
34. HR WPAN (IEEE 802.15.3)
IEEE 802.15.3 is a standard for high rate (11-55 Mbps) WPANs.
Adhoc n/w
It is also similar to Bluetooth that specifies MAC/ PHY layer only.
Focus on: Qos, Security, power management
The main purpose is to provide:
1. Low cost
2. Low complexity
3. Low power consumption
4. High data rate connectivity for wireless personal devices.
It supports the data rate of at least 11 Mbps data rate within at least 10m range.
The vision is to “to promote wireless multimedia connectivity and interoperability between devices in a
personal area network”.
35. A multimedia solution need to have following characteristics:
1. Simplicity of use.
2. Advanced Qos
3. Low complexity
4. Low cost
5. Support long battery life
6. Sufficient data rate
7. A scalable security platform
8. High bandwidth
9. Secured network
36. Reference Model
Reference model of IEEE 802.15.3 deals with the protocol stacks for WPAN multimedia networks.
Applications
Transport Control
802.15.3 MAC
802.15.3 PHY
37. PHY layer:
Transmission is based on impulse radio.
2 technology: DS UWB, OFDM
11 Mbps-55 Mbps
MAC layer:
Network toplology of IEEE 802.15.3 closely resembles that of Bluetooth:
HRPAN is called piconet and it is composed of a set of devices logically associated to a piconet
coordinator.
Piconet coordinator is responsible for: managing Qos, power save modes, access control, assign time slots
to each device and distribute payload protection keys.
38. 3. Transport profile:
Includes transport of media packets, signalling (link establishment and negotiation of streaming
parameters) and monitoring (application parameter adapted to radio link quality).
4. Control profile:
control profile standardizes the control of all type of interfaces.
39. LR-WPAN (IEEE 802.15.4): Zigbee
The IEEE 802.15.4 task group focussed on:
1. Low data rate
2. Having the battery life ranging from months to several years
3. Low complexity
1 channel-868 Mhz, 10 channel 915 Mhz, 16 channels 2.4 Ghz
The range is 10-75m
40. Zigbee Components and Topology Models
A zigbee has several components.
The basic one is device.
A device can be Full Function Device (FFD) or Reduced Function Device (RFD).
A network shall include atleast 1 FFD (WPAN coordinator).
FFD can operate in 3 modes: a cordinator, a router or a device.
RFD is intended for simple applications that do not need to send large amount of data.
An FFD can communicate to RFDs or FFDs.
Whereas an RFD can communicate to an FFD.
