Wireless Home Automation Networks: A Survey of Architectures and Technologies Carles Gomez and Josep Paradells Presented by Deepen Solanki and Aishwarya Rao Table of Contents 1. Introduction to WHANs 2. Solutions for WHANs a. ZIGBEE b. Z - WAVE c. WAVENIS d. INSTEON e. IP BASED 3. Discussion 4. Conclusion INTRODUCTION - WHANs WHAN Connectivity Monitoring Control Sensors Actuators ● Remote Control of Devices - Appliances ● Remote Care - wearables, fall detection ● Smart Energy Monitoring - HVAC, usage patterns ● Security Systems - burglar alarm, smoke detection INTRODUCTION - WHANs Characteristics ● High node density - (100s) ● Multipath environment - multiple reflective surfaces ● Interference - Bluetooth devices, microwave ovens ● Multihop communications - combating range ● Self-healing network - mobile devices ● Various traffic patterns - P2P, P2MP, MP2P ● Quick results - emergency situations ● Internet connectivity - Remote monitoring ● Highly constrained nodes - memory, processing power SOLUTIONS FOR WHANs ● ZigBee ● Z-Wave ● INSTEON ● Wavenis ● IP Based Solutions ZIGBEE (2004) ● Low Data Rate - 20, 40, 250kbps ● Short Range - 10 to 100m ● Bands - 868MHz / 915MHZ / 2.4GHz ● DSSS ● Device types Coordinator End device Router Beacon ● Channel access ● Profiles Beaconless ● Tree, Mesh ZigBee Home Automation Public Application Profile ZigBee Smart Energy Profile Z-WAVE (1999) ● Reliable transmission of short messages from a control unit to one or more nodes in the network ● 868.42 MHz in Europe, 908.42 MHz in US, 2.4GHz* ● Low data rate - 9.6kb/s, 40kb/s, 200kb/s* ● MAC Layer - CSMA/CA ● Source-routed mesh network ● Range - 90m outdoor, 20m indoor ● Device types Controller End device ● primary / secondary ● blindly execute commands ● initiations, retransmissions ● routing slaves and static tables ● routing tables ● exclusions, node IDs WAVENIS ● Low-power, long-distance wireless communications ● Data rates between 4.8kb/s and 100kb/s ● 433MHz, 868MHz, 915MHz, 2.4GHz Synchronous CSMA/TDMA ● MAC Layer Non - synchronous CSMA/CA ● Only one type of device, virtual tree hierarchy New device → Broadcast request → QoS → Joined! http://www-coronis-com.dyn.elster.com/downloads/Wavenis_Data_Sheet_A4_CS5.pdf INSTEON (2005) ● Dual mesh topology ● Links between devices can be either RF lines, power lines or both ● FSK, 904MHz, 38.4kb/s ● All devices are peers ● Not in range? → time-synchronized multihop ● Simulcast → devices within same range can transmit messages simultaneously IP-BASED SOLUTIONS ● IPSO Alliance ● IPv6 over Low power Wireless Personal Area Networks → 6LoWPAN ● Fragmentation, Header compression, address auto-configuration, neighbor discovery ● Organization ○ Edge router = the bridge ○ Mesh router ○ Nodes http://www.ti.com/lit/wp/swry013/swry013.pdf IP-BASED SOLUTIONS http://www.ti.com/lit/wp/swry013/swry013.pdf DISCUSSION Physical Layer Modulation and Spread-Spectrum Techniques ● FSK- easy to implement, used by Z-Wave and INSTEON ● GFSK- greater spectral efficiency than FSK, used by Wavenis ● PSK- More complex but better SNR, used by ZigBee ● Spread Spectrum techniques provide protection against multipath and narrowband interference- ZigBee and Wavenis DISCUSSION Single Channel vs. Multichannel ● ZigBee coordinator can decide to re-form the whole network in a new channel if severe interference is detected by any node ● Single channel sub gigahertz operation exploits lower susceptibility to interference than 2.4GHz band to simplify hardware design DISCUSSION Link Layer Reliability: ● Z-wave and INSTEON use 8-bit checksum ● ZigBee and 6LoWPAN use 16-bit checksum ● Optional link layer ACKs for reliable link transmission Delay: ● For reliable mode, the roundtrip time including transmission of an ACK is provided ● 900 MHz channels DISCUSSION Network Layer Routing/Multihopping State ● Z-Wave- only the controller stores and maintains a routing table ● ZigBee- recommends the use of large routing tables due to high density expected in a residential scenario, which increases memory requirements on nodes ● Wavenis- each device only stores its own route to the root, root stores the routes to reach each node ● INSTEON- use simulcast instead of routing, avoids the need to store state for multihop communications DISCUSSION Routing Metrics ● ZigBee and 6LoWPAN use link quality indicator (LQI) offered by IEEE 802.15.4 ● Wavenis uses a link quality estimator based on RSSI- may not be accurate due to interference and multipath Route Change Latency ● INSTEON uses simulcast instead of routing so doesn't suffer from a connectivity gap ● Other solutions experience the latency for detecting the link failure and finding an alternative path ● 1s for Z-wave, 50-100ms for ZigBee DISCUSSION End to End Reliability ● ZigBee filters duplicate packets ● In 6LoWPAN, use UDP augmented with sequence numbers, ACKs, and retries Application Layer ● ZigBee, Z-Wave, and INSTEON - well defined commands and attributes for various WHAN applications DISCUSSION Security ● ZigBee, Z-Wave 400 series, Wavenis and 6LoWPAN- 128-bit key Advanced Encryption Standard (AES) algorithm ● INSTEON offers various encryption methods but recommends the use of simple rolling-code encryption Internet Connectivity ● 6LoWPAN is intrinsically interoperable with the Internet- avoids issues in terms of security, management, and consistency in QoS policies DISCUSSION Implementation Size ● ZigBee, Z-Wave, and INSTEON implement protocol architectures up to application-layer functionality ● Zigbee requires largest footprint, INSTEON requires least memory ● Wavenis consumes a small amount of RAM but requires a medium flash memory size ● 6LoWPAN implementations require less ROM/flash than ZigBee, Z-Wave, and Wavenis Standardization and Market Adoption ● 6LoWPAN unlike the others is open, and its implementation does not require a license ● ZigBee products in the market has been delayed in comparison with those based on other solutions ● Smart Energy Version 2 - providing end-to-end connectivity between energy providers and consumers CONCLUSION ● ZigBee and 6LoWPAN were designed for general purposes ● Other solutions were developed for specific application ● Trend in converging toward IP- future WHAN applications will benefit from enhanced quality, security, and interoperability. 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