IT800SCP Power Line Communications (PLC) Processor - Infrastructure for the Connected Smart Home

Transcription

1 IT800SCP Power Line Communications (PLC) Processor - Infrastructure for the Connected Smart Home Dr. Oren Kaufman*, Asaf Avidan** * Ph.D., M.B.A Regional Manager East Asia & Pacific ITRAN Communications Ltd. - Osaka Office C/O Preminet, 3-12, Hinjohigashi 2-chome,Kita-ku, Osaka, Japan, Phone: , Fax: oren@itrancomm.com ** BSEE, LL.B Customer Support Manager ITRAN Communications Ltd. Headquarters 9 Yehoshua Hatsoref st., Beer Sheva, Israel, Phone: , Fax: asafa@itrancomm.com Abstract The IT800SCP Power Line co-processor incorporates in a single ASIC, Microsoft s Simple Control Protocol (SCP) stack and ITRAN s extremely robust IT800 command/control power line carrier modem. SCP is a very lightweight device control protocol that allows manufacturers to create small, intelligent devices that can communicate with each other, securely and robustly, in narrowband communication networks. With the IT800SCP chip, simple devices with limited computing power and memory resources such as light switches, alarm clocks and appliances can participate in a peer-to-peer network of other SCP-enabled devices, and can also participate in more sophisticated Universal Plug and Play (UPnP) networks, through a UPnP-to-SCP Bridge. The key features of the SCP are: simple; efficient device control implementation; peer-to-peer networking; optimized for lightweight devices and narrowband control networks; full UPnP interoperation through automatic bridge; automatic device discovery; simple messaging semantics; reliable broadcast and point-to-point communications; selectable security levels; presence tracking and multiple logical networks. 1. Introduction The concept of implementing a no new wire home network over the existing electrical wiring is very attractive, but its realization introduces very demanding challenges, both at the Physical layer (PHY) and the upper layers (Data Link Layer, Networking Layer and Transportation Layer). Power line communication solutions are available from various vendors for more then 20 years, but some of them are known for lack of performance and others for the complicated installation schemes. Within the variety of different proprietary solutions there are always questions about co-existence and security. From the PHY point of view, the home networking solution should have close to 100% coverage and provide robust and reliable communication. Protocol related issues are peer-to-peer networking, network management, device acquisition, security, diagnostics, network configuration and many others. Microsoft and ITRAN provide the optimized solution to all the issues mentioned above, introducing the IT800SCP PLC Processor, incorporating Microsoft Simple Control Protocol (SCP) running on top of ITRAN S IT800 PHY and DLL.

2 2. Simple Control Protocol Microsoft s SCP is a device control protocol for simple devices with limited calculating power and memory operating in narrowband communication networks (such as home control and automation). It allows manufacturers to create small, intelligent devices that can communicate with each other, securely and robustly. SCP is media agnostic, although its first implementation is targeted at narrowband Power Line Carrier (PLC) control networks. TheIT800SCP chip is designed to be controlled by the device application processor, which can be as simple as a low-end eight-bit PIC chip. With IT800SCP, simple devices with limited computing power and memory resources such as light switches, alarm clocks and appliances can be part of a peer-to-peer network of other SCP-enabled devices, and can also participate in more sophisticated Universal Plug and Play (UPnP) networks through a UPnP-to-SCP Bridge. The home automation industry shows rapid growth and with it also intensive competition between proprietary device control protocols and physical layer vendors, which brings the fragmentation to extreme. The existing protocols and physical layer implementations are either too difficult to configure and use or not reliable enough to provide a consistently good user experience, or both. Devices from one vendor do not interoperate with those of other vendors - in fact, one product may actually prevent other products from operating on the same physical medium. This fragmentation, poor performance and lack of interoperability and co-existence limit the dispersion of the home automation market. Microsoft s intention in the development of SCP has been to help jump-start home automation by unifying the market at two levels. At the protocol level, Microsoft provides a robust, secure, efficient and royalty-free protocol (SCP). At the physical medium level, Microsoft licenses SCP for usage with various physical layer technologies, which are shown not to interfere with one another. As part of the SCP licensing terms, physical layer vendors must make their technology available on a non-discriminatory basis to any organization wishing to license it. As a result, homeowners can be sure that no matter whose SCP-based products they buy, the devices will be compatible with each other. The list of the SCP key features is presented below: Application and Network Control Protocols - SCP consists of two separate protocols: the Application Protocol (AP) for normal device messages, and the slower but very robust Network Control Protocol (NCP) used to assign network ID and device ID and to perform other network management and diagnostic functions. Typically, Microsoft s Address Space Arbitrator (ASA) SCP entity assigns the network ID and device ID. Peer-to-peer networking - once an SCP device is assigned its network ID and device ID, no central control device is further required for routing messages. All communication takes place directly between devices, eliminating single points of communication failure. Optimized for low-speed control networks - SCP messages are compact and require minimal header information. The device control and messaging semantics are designed to minimize network traffic. For example, devices can detect the fact that an associated device is no longer in the network and stop trying to send messages to that device, avoiding unnecessary network traffic. When the device is reconnected to the network, the relationships to other devices re-establish themselves. Automatic device discovery this feature simplifies adding new devices to the SCP network and allows

3 devices to self-recover from a power outage. Devices retain, in persistent storage, their network IDs and their relationships to other SCP devices. When power is restored the devices automatically re-establish their relationships with other devices. Simple messaging semantics - SCP uses Properties, Property Values and Property Routes for inter-device communication. To change a device s behavior you just change the software property relationships between devices. So just by changing a simple property value your alarm clock can start your coffeemaker based on the alarm time. Or the security panel can turn off lights and appliances automatically when you leave the house. Broadcast and reliable point-to-point communications - SCP devices can send messages point-to-point, request acknowledgements to verify message delivery, or broadcast messages to all the devices with or without acknowledgements. These features allow the appropriate tradeoffs to be made between message reliability and network loading. Network media independence - Although the initial implementation of SCP supports networking over a Power Line Carrier (PLC) transport, the protocol is designed to be media-agnostic. Infrared (IR) and radio frequency (RF) are potential future transports. UPnP interoperation - SCP devices use the same device models and schemas developed by the Universal Plug and Play (UPnP) Forum, allowing SCP and UPnP devices to interoperate easily through a Bridge. This extends the full capabilities of UPnP into the world of small devices, which can t afford the cost of a TCP/IP and native UPnP stacks and the required processing power. For example, SCP device properties can be set through messages sent across the Internet. All SCP device property relationships are established at the UPnP level through the Bridge and propagate down to the SCP network and device level. UPnP bridging also allows SCP devices to interoperate with devices that use other control protocols. If a Bridge exists between those devices and a UPnP network then SCP devices can use UPnP as a common communication language. Selectable security levels - The SCP network can operate at one of three security levels: no security, medium security or high security. Medium and High are key-based security modes providing 128-bit encryption of each SCP message, as well as jamming of imposter messages. Much as an anti-virus program detects suspicious activity, a separate security component can use SCP security capabilities to identify and jam devices that originate suspicious device commands. For example, messages from a sprinkler head could be jammed if the sprinkler attempts to control the home security panel. Presence tracking - SCP nodes monitor all other nodes with which they have relationships. If any of those nodes fails or is powered off, the associated nodes detect this condition and stop sending messages to the disabled nodes. This reduces unnecessary network traffic. When a node returns to the network, its relationships with other devices are re-formed and communications return to normal. Simple and efficient IT800 based PLC device implementation - The SCP over power line implementation is delivered as an integrated single chip (the IT800SCP), to which the device developer needs to add a simple application processor (to process the native device logic and to control the IT800SCP chip) and an EEPROM (typically about 500 bytes) to store client-side

4 device property relationships and other persistent information. The IT800SCP chip provides an SPI hardware interface to allow control by the device application processor. The detailed description of the IT800SCP chip is presented in the next section Multiple logical networks - SCP supports a two-level address space, which allows for the formation of several logical networks within a single physical network. For example, adjacent homes and apartments typically share a physical power line network, since they are wired to the same electrical power transformer. SCP allows each household to create its own separate logical network on the shared physical network, to prevent devices in one home from being controlled by a neighboring device. SCP security allows logical networks operating on the same physical medium to be securely isolated from one another. SCP supports approximately 1000 logical subnets per physical network and approximately 2000 devices per logical network. Extensive diagnostic support - For product development, testing and debugging, installation, and ongoing support, a set of support tools enables the developer to view SCP/PLC messages on the wire, send ad-hoc messages to devices, and manually establish property routes between devices. The protocol itself also includes an extensive set of diagnostic support features. For example, a device can test the quality of communications between itself and another network node, or a third-party device can tell two nodes to test their communication path. This function can be performed at the Application Protocol and the Network Control Protocol levels. Configurable network parameters - SCP allows setting of network timing and modal parameters retry settings, X10 coexistence flags, and other network variables. SCP also provides access to network statistics, such as bit error rates. The features listed above show the wide range of capabilities presented by the SCP and provide solutions to most of the known requirements of control protocols. 3. IT800SCP PLC Processor IT800SCP incorporates, in a single ASIC, Microsoft Simple Control Protocol (SCP) stack and ITRAN S robust IT800 command/control power line carrier PHY and DLL. The IT800 PHY is a highly reliable power line transceiver implementation, possessing extremely high in-phase and cross-phase reliability. Implementing ITRAN S patented spread spectrum DCSK (Differential Code Shift Keying) modulation technique, the IT800 modem core enables robust communication with data rates up to 7.5Kbps. The main features and benefits of DCSK are: close to theoretical reliability limits over Additive White Gaussian Noise (AWGN); improved resistance to pulsed noise and narrow-band interference; resistance to fast variations in line characteristics; short synchronization time; resistance to synchronization errors and timing jitter and fast recovery from severe fade or jamming. In addition to the inherent interference immunity of the DCSK modulation, the device utilizes several mechanisms for enhanced communication robustness such as forward short block soft decoding error correction algorithms and special synchronization algorithms. UART interface enables simple seamless connection to an external Host for a low cost robust total solution. ITRAN S DLL (Data Link Layer) is optimized for PLC and enables full utilization of the PHY. The main features of the DLL include support for up to 1023 logical networks

5 with up to 2047 nodes per network, Acknowledged, unacknowledged and repetitive unacknowledged services (packet transmission and reception), retransmissions mechanism (acknowledged and unacknowledged), Supports for all PHY transport modes with adaptive rate control (1.25Kbps 7.5Kbps), CSMA/CA (Carrier Sense Multiple Access with Collision Avoidance) channel access scheme, Adaptive back-off algorithm based on IEEE with adaptation to the power line medium (patent pending) and more. The IT800PSCP is configurable to comply with worldwide regulations (such as FCC part 15, ARIB and CENELEC bands). Summary World leading companies such as Matsushita (National) and Mitsubishi have already chosen to adopt and implement SCP. Mitsubishi Electric has announced the development of its own SCP PLC Processor, which embeds ITRAN S IT800 PHY and an M16C MCU that runs the DLL and SCP stack. This chip (M306S) will be compatible with ITRAN S already available IT800SCP. Both chips incorporate all the advantages of the IT800 power line communication PHY and DLL technology, which assures robust and reliable communication over existing electrical wires ( No New Wires technology). Together with the unique abilities of SCP, the most advanced and effective command/control protocol, the IT800SCP device an ideal solution for a wide variety of command and control applications. Note all trademarks mentioned herein are the property of their respective owners.