CS526 Wireless Sensor Networks ZigBee/IEEE 802.15.4 Overview KD Kang 9/21/2018 CS526 Wireless Sensor Networks

WPAN (Wireless Personal Area Network) Cellular networks A cell covers a large area (1-2 km) A smaller coverage is needed for higher user densities and emergent data traffic IEEE 802.11 Ethernet matching speed, Long range (100m) High data rate WPAN Wireless network around a person (10m) Low-cost, low-power, short range, very small size 9/21/2018 CS526 Wireless Sensor Networks

CS526 Wireless Sensor Networks WPAN classes High data rate WPAN 802.15.3 20 Mbps or higher Multimedia applications with high QoS needs Medium rate WPAN IEEE 802.15.1/Bluetooth Cell phones – PDA communication Voice communication: 1 – 3 Mbps Low rate WPAN (LR-WPAN)  IEEE 802.15.4/ZigBee Industrial, residential, and medical applications Low-power, low-cost Relaxed need for data rate and QoS: 20kbps – 250kbps 9/21/2018 CS526 Wireless Sensor Networks

CS526 Wireless Sensor Networks ZigBee vs. Bluetooth ZigBee Can implement mesh networks larger than is possible with Bluetooth ZigBee compliant device transmit 10 – 75 meters (Bluetooth device can transmit 10m) Low data rate in unlicensed RF worldwide 2.4GHz global: 250kbps 915MHz in Americas: 40kbps 868MHz in Europe: 20kbps Low frequency provides longer range due to lower propagation losses 9/21/2018 CS526 Wireless Sensor Networks

CS526 Wireless Sensor Networks IEEE 802.15.4/ZigBee ZigBee is a low data rate, low power, low cost wireless networking protocol targeted towards automation and remote control applications IEEE 802.15.4 committee started working on a low data rate standard a short while later ZigBee alliance and IEEE joined forces ZigBee is the commercial name IEEE 802.15.4 standard more focused on Physical and MAC layers 9/21/2018 CS526 Wireless Sensor Networks

CS526 Wireless Sensor Networks ZigBee devices Full function device (FFD) A network has at least one FFD operating as the PAN coordinator Can operate as a PAN coordinator, router, or device Only one coordinator in a PAN Can communicate with RFDs and FFDs Reduced function device (RFD) End device Can only talk to FFD 9/21/2018 CS526 Wireless Sensor Networks

CS526 Wireless Sensor Networks Network Topologies 9/21/2018 CS526 Wireless Sensor Networks

CS526 Wireless Sensor Networks Star topology Communication is established between devices and a single PAN coordinator Applications: home automation, personal computer peripherals, toys & games After an FFD is activated for the first time, it may establish its own network and become the PAN coordinator Each star network has a unique PAN ID 9/21/2018 CS526 Wireless Sensor Networks

Mesh/P2P (peer-to-peer) topology Unlike a star PAN, FFDs can directly talk with each other as long as they are in a communication range of one another Applications: industrial control and monitoring, WSNs, … Multipath routing is possible for reliability 9/21/2018 CS526 Wireless Sensor Networks

Cluster-tree topology A special case of a P2P network Most devices are FFDs Any FFD can be a coordinator, but only one of them is the PAN coordinator The PAN coordinator forms the first cluster by establishing itself as the cluster head (CLH) with cluster ID (CID) 0, choose an unused CID and broadcast beacon frames to neighboring devices A device receiving the beacon may request to join the network at the CLH The coordinator may instruct a device to become the CLS of a new cluster Increased coverage at the cost of increased message latency 9/21/2018 CS526 Wireless Sensor Networks

CS526 Wireless Sensor Networks IEEE 802.15.4 MAC 9/21/2018 CS526 Wireless Sensor Networks

CS526 Wireless Sensor Networks Superframe structure Superframe bounded by network beacons from the coordinator Divided into 16 equally sized slots: Structure defined by coordinator Beacon sent in the first slot of each superframe to synchronize devices, to identify PAN, and describe superframe structure Optional: Coordinator can turn off beacon transmissions, if it doesn’t want superframe structure 9/21/2018 CS526 Wireless Sensor Networks

Optional Frame Structure Inactive Period 15ms * 2SO where 0  SO  14 Active Period 15ms * 2BO where SO  BO  14 Beacon Interval SO = Superframe order BO = Beacon order Superframe may have inactive period If superframe structure is not used, coordinator does not transmit a beacon and set BO = SO = 15  All transmissions except ACK will use unslotted CSMA-CA Source: Marco Naeve.

Optional Superframe Structure: Active portion = CAP + CFP with Guaranteed Time Slots GTS 1 GTS 2 GTS 3 Contention Access Period Contention Free Period Slot 15ms * 2n where 0  n  14 Network beacon Transmitted by PAN coordinator. Contains network information, frame structure and notification of pending node messages. Beacon extension period Space reserved for beacon growth due to pending node messages Contention Access by any node using slotted CSMA-CA Guaranteed Time Slot Reserved for nodes requiring guaranteed bandwidth [n = 0]. Source: Marco Naeve, Eaton Corp.

CS526 Wireless Sensor Networks CSMA-CA CSMA-CA is not used in two cases: Channel access during CFP If a device requests data from the coordinator, the coordinator immediately send ACK followed by data If superframe structure is used, use slotted CSMA-CA: similar to CSMA-CA in 802.11 Else, use unslotted CSMA-CA: more aggressive than slotted CSMA-CA 9/21/2018 CS526 Wireless Sensor Networks

Slotted CSMA Procedure 05 2004 Used in beacon enabled networks. Source: Marco Naeve

Un-slotted CSMA Procedure 05 2004 Used in non-beacon networks. Source: Marco Naeve

CS526 Wireless Sensor Networks Routing: AODV RREQ RREP RERR Hop count Sequence number 9/21/2018 CS526 Wireless Sensor Networks

Routing: Single cluster network 9/21/2018 CS526 Wireless Sensor Networks

Routing: Single cluster network – Multihop cluster setup 9/21/2018 CS526 Wireless Sensor Networks

Routing: Multiple cluster network Designated deivce (DD) Assign a unique cluster ID to each cluster head 9/21/2018 CS526 Wireless Sensor Networks

CS526 Wireless Sensor Networks 9/21/2018 CS526 Wireless Sensor Networks

CS526 Wireless Sensor Networks More information S. C. Ergen, ZigBee/IEEE 802.15.4 Summary, Sept. 10, 2004. IEEE 802.15 Working Group for WPAN http://www.ieee802.org/15/ ZigBee Allicance http://www.zigbee.org/ 9/21/2018 CS526 Wireless Sensor Networks

CS526 Wireless Sensor Networks Questions? 9/21/2018 CS526 Wireless Sensor Networks