EE5412 assignment

EE5412 assignments : v1.3 7 April 2010 Antigone

Discuss the difference between Bluetooth and ZigBee network in terms of objective, topology, protocol architecture etc.

Bluetooth and ZigBee are two widely used wireless communication standards. This paper will compare the difference in terms of objective, topology and architechture.

Objective:

Bluetooth is an open specification for short range integrated wireless voice and data communication. It can provide a universal short-range wireless capability. Bluetooth uses the 2.4-GMHz band, with two Bluetooth devices within 10m ofeach other, each can share up to 720 kbs of capacity.

According to the ZigBee allicance , Zigbee is a very low-cost, very low-power-consumption, two-way, and wireless communications standard. It is easy and inexpensive to deploy and the unlicensed IMS radio bands. It aims to build a sel-organizing mesh network that address the unique needs of most remote monitoring and control sensory network applications.


Topology : Bluetooth has a scattered ad hoc topology, that is, a number of small networks support a few terminals to co-exist or interoperate with one another.
A Bluetooth network is self-configurable. It provides an easy way to form a new small network and a procedure for participation in an existing one.

The terminals have options to associate with multiple Bluetooth networks at the same time.

In Bluetooth, the basic unit of networking in Bluetooth is a piconet. It consists of one master and up to seven active slave devices. The radio designated as the master makes the determination of the channel (frequency-hopping sequence) and phase (timing offset, ie, when to transmit) that shall be used by all devices this piconet.

A slave may only communicate with the master and may only communicate when granted permission by the master. A device in one piconet may also exist as part of another piconet and may function as either a slave or master in each piconet.

This is the concept of scatternet. the advantage of the piconet/scatternet scheme is that it allows many devices to share the same physical area and make efficient use of the bandwidth. A Bluetooth system uses a frequency-hopping scheme with a carrier spacing of 1 MHz. In general, there can be up to 80 different frequencies are used for a total bandwidth of 80 MHZ.

Insead of a scatternet, the ZigBee network layer supports star, tree and mesh topologies.

In a star topology, the network is contolled by the ZigBee coordinator. The ZigBee coordinator is responsible for initiating and maintaining the device on the network. all other devices are known as end devices. In mesh and tree topologies, the network is extended by the ZigBee router. Mesh network allow full peer-to-peer communication. A mesh network contains a single coordinator, and multiple routers and end devices.



protocol architecture :

Bluetooth has a layered protocol architecture. It consists of core protocols, cable replacement and telephony control protocols, and adpoted protocols. The core protocolcomprises five layers, namely Raido, Baseband, Link manager protocol (LMP), Logical link control and adaptation protocol (L2CAP) nad the service discovery protocol (SDP).

The radio layer specifies details of the air interface, including frequency, the use of frequency hopping, modulation scheme, and transmit power. The baseband layer states the connection establishment within a pconet, addressing, packet format timing and power control. The link manager protocol (LMP) is responsible for link setup between Bluetooth devices and ongoing link management. This inclues security aspects such as authentation and encryption, plus the control and negotiation of baseband packet sizes.

The logical link control and adaptation protocol (L2CAP) laver adapts upper-layer protocols to the basseband layer. L2CAP provides both connectionless and connection-oriented services. The srvice discovery protocol (SDP) specifies device information, services, and the characteristics of the services can be queried to enable the establishment of a connection between tow or more Bluetooth devices.

For the cable replacement protocal layer, radio frequency communication RFCOMM is used. RFCOMM presents a vitual serial port designed to replace cable technologies. It provides binary data transport and emulates EIA-232 control signals over the Bluetooth baseband layer.

Bluetooth specifies a telephony control protocol. TCS BIN (telephony control specification--binary) is a bit-oriented protocol that defines the call control signal for the establishment of speech and data calls between Bluetoth devices. Also, it defines mobility management procedures for handling groups of Bluetooth TCS devices.

The adpoted protocols are defined in specifications issued by other organization and icluded in the overall Bluetooth architecture. There are four protocols being adopted, namely PPP (point-to-point protocol), TCP/UDP/IP, OBEX(Object exchange protocol), and the WAE/WAP protocol.

As to ZigBee, it builds on top of the physical (PHY) and medim access control (MAC) sub-layer as specified by the IEEE802.15.4 standard. ZigBee provides the network (NWK) layer and the framework for the appliation layer. The application layer framework consists of the application support sub-layer (APS) and the ZigBee device object (ZDO).

The network layer handles network address and routing by invoking actions in the MAC layer. Its task include starting th network (coordinator), assigning network address, adding and removing network devices, routing messages, applying security and implementing route discovery.

The ZigBee security sevice Provider (SSP) provides security mechanism for layers that use encryption. Also, application support (APS) sublayer is responsible for providing a data service to the application and ZigBee device profile. In addition, the ZDO management plane facilitates communication between the APS and the NWK layers with the ZDO.

The ZigBee Device Object (ZDO) defines the role of a device within the framework (coordinator, router or end device). It also initiates and responds to binding and discovery request.

ZigBee Application objects are software at an endpoint that controls the ZigBee device. A single ZigBee node supports up to 240 application objects.

The application framework describes how to build a profile onto a ZigBee tack. Finally, the top layer is the application layer (APL)

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