Presented By
MANOJ SUDHARSHAN J

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Congestion Control for Efficient Transmission in ZigBee Networks
INTRODUCTION
 ZigBee is a leading wireless network technology with low cost, low power based on IEEE 802.15.4
 Recently, ZigBee networks are rapidly developed because of its low cost, low power and high reliability characteristic
 Congestion control is necessary technique in order to guarantee a reliable transmission and network efficiency
 ZigBee provides retransmission and acknowledgment (ACK) to prevent data loss instead of congestion control. It could prevent congestion situation rather than control it.
 When congestion occurs there is no mechanism to control it in ZigBee. Only using retransmission and ACK, ZigBee prevents congestion
NEED OF ZIGBEE
 Installation cost
 Maintenance
 New markets
ZIGBEE BENEFITS
 Low Cost
 Range and obstruction issues avoidance
 Multisource products
 Low power consumption
STACK ARCHITECTURE OF ZIGBEE PROTOCOL
 Network and Application Support layer
 Physical (PHY) layer
 Media access control (MAC) layer
ZIGBEE DEVICE TYPES
 The ZigBee coordinator node
 The full function device FFD
 The reduced function device RFD
NETWORK LAYER AND TOPOLOGY OF ZIGBEE
 The Zigbee network layer (NWK) supports star, tree and mesh topologies
• Modes of Traffic in Zigbee
 ZigBee employs either of two modes to enable the to-and- fro data traffic
1. Beacon Mode
2. Non-Beacon Mode
CURRENT ZIGBEE TECHNOLOGY
 In Zigbee technology each node forms the topology and network configuration. Thus each node can freely send and receive data.
 All collected data will be sent to the sink node. Getting closer to the sink node, network traffic will increase.
 Also ZigBee networks provide the ACK and retransmission functions to ensure the reliability of data. These functions are kind of congestion avoidance
• Successful data transmission with an ACK
• Retransmissions are failed – The worst case
PROPOSED CONGESTION CONTROL
1. ZCCF (ZigBee Congestion Control Frame)
Network Congestion Case # 1 Network Congestion Case # 2
2. ZTCC (ZigBee Time Congestion Control)
 When the originator receives ‘Congestion reply command’ or ‘Congestion announce command’, a transmission time is increased as shown in (1) below. We define the time value-apscThresholdTime.
 After apsCongestionTime value is greater than the threshold value, it will be increased linearly as shown in (2).
apsCongestionTime = apsCongestionTime • 2. (1)
apscThresholdTime = apscThresholdTime + 20. (2)
 To stabilize the networks, we use the ACK Command
 When the originator receives the ACK, it confirms congestion bit. If the congestion bit is 1, the originator will changes a transmission time as shown in (3) and a threshold time value as shown in (4).
apsCongestionTime = apsCongestionTime / 2. (3)
apscThresholdTime = apscThresholdTime – 100. (4)
 As a result, when congestion situation is over, a data transmission time is returned to the original value. The threshold time is back to the default value after 5 continuous ACKs
SIMULATION RESULTS
 The compartment of the ZBN and CCZ in the many-to-one communication application is shown.
 As shown in Fig, as the number of nodes increases, CCZ acquires performance of less transmission time than the ZBN when transmitting 50Kbytes data.
 The period of the whole communication is considered as the transmission time.
 When the quantity of nodes is equal 100, by the use proposed congestion control, the CCZ network speed is improved about 9.31% than the ZBN.
 The simulation results show us that the proposed ZigBee APS layer has a performance improvement.
GENERAL CHARACTERISTICS OF ZIGBEE
• Data rates from 20 to 250 kbps
• Star Topology/Peer to Peer (mesh)
• 255 devices / network
• CSMA-CA Access Scheme
• Enumeration (new node) ~ 15-30 ms
• Dual PHY (868/915 MHz, 2.4 GHz), DSSS
• Range: 10-100 m
• Low Duty Cycle (< 0 .1%, TX)
• Low Power Cons, +1 year battery life time
• Complexity: 4 -32 kB (protocol)
APPLICATIONS OF ZIGBEE
 Home Entertainment and Control
 Home Awareness
 Mobile Services
 Commercial Building
 Industrial Plant
CONCLUSION
 Zigbee provides a promising wireless network for a small area network
 Zigbee provides an advantage of range and obstruction.
 There are many standards like Bluetooth and Wi-Fi which provide mid and high data rates, but zigbee provides a unique network of low data rates and, cost effective radios and low power consumption circuits.
 In reference to the ieee paper, we have confirmed that ZigBee does not provide separate congestion control yet.
 When congestion occurs in ZigBee networks, unnecessary traffic as well as unreliable data transmission increases power consumption.