Archive for the ‘Bluetooth’ Category

WiGig Tempts With High-Speed Wireless Data Transfer

Wednesday, June 24th, 2009

Cables

A new standard aims to offer gigabit-speed connectivity without the clutter of cables.

“What we are talking about here is the ability to download a 25 GB Blu-ray disc in under a minute,” says Mark Grodzinsky, chairman of the marketing workgroup at the Wireless Gigabit Alliance. “It’s not something you can do with Wi-Fi or any other standard right now.”

The Wireless Gigabit Alliance, a consortium of electronics companies, has established a specification for 60 gigahertz wireless technology that can offer users data transfer speeds ranging from 1 Gigabits per second to 6 Gbps. To put it simply, WiGig could be at least ten times faster than today’s Wi-Fi and it could be available to consumers by the end of next year.

The need for fast wireless data transfer plays into two big trends: the proliferation of multimedia and the increasing cable clutter than users have to deal with.

Users are increasingly getting hooked on Hulu, browsing through Flickr and clicking on YouTube shorts. But for all their new streaming media players or cameras, consumers haven’t been able to cut the cord.

Take the set-top box in today’s home that has to be connected to the TV through an HDMI cable. “This is one of those technologies that almost 100 percent uses a wire because the speeds required to stream a high-def 1080p video is at least 3 Gbps,” says Grodzinsky, “and no wireless technology today can do that across multiple applications.”

That’s where WiGig could step in. The standard will allow for extremely fast file transfers, wireless displays, streaming media, and wireless connections for devices such as cameras, laptops and set-top boxes among other things, says the Alliance. It won’t have the same range as a Wi-Fi network but it is ideal for devices that want to communicate without wires at gigabit speeds within a room or adjacent rooms, says Grodzinksy.

“Today’s wireless networks will top out at a few hundred Mbps but what we are talking about here is multiple gigabits of data transfer speed,” says Craig Mathias, principal with research firm Farpoint Group. “That plays into the ever-increasing demand for throughput.”

WiGig joins a fray of wireless standards that are fighting to free consumers from being tethered to their devices.  In most homes, Wi-Fi has emerged as the standard technology for wireless access. But it is too slow to handle high-definition video or transfer pictures from the camera to the laptop.

Wireless Standards & Data Speeds

802.11g Wi-Fi: The basic and most widely used Wi-Fi connectivity offers speeds of up to 54 Mbps.

802.11n Wi-Fi: The faster W-Fi standard it offers data transfer at up to 300 Mbps.

Standard Bluetooth: Most widely used between cellphones and headsets, it offers top transfer rate of about 3 Mbps.

Bluetooth 3.0: The ‘high-speed’ successor to standard Bluetooth, its top transfer rate hover around 24 Mbps.

Wireless USB: It can offer speeds of up to 110 Mbps  at a range of 10 meters and 480 Mbps over a range of 3 meters.

Wireless HD: Aimed at HD video transfer it can offer speeds of up to 4 Gbps (for 10 meters). Theoretical speed can go up to 25 Gbps.

WiGig: The newest kid on the block tantalizes with promise of speeds ranging from 1 Gbps to 6 Gbps.

Zigbee: This low-power wireless standard is for applications that require low data transfer but quicker response time such as remote controls.

Meanwhile, other standards such as wireless HD and Zigbee have sprung up offering to solve these problems. But they just aren’t broad enough to be used across multiple applications. Take wireless HD. Despite its promises of high speed connectivity, it is largely seen as a vehicle for high-def video transfer.

WiGig has a bigger umbrella, says Grodzinsky. “We want to be more than simple cable replacement,” he says. “We want complete interoperability and be on a number of platforms from TVs to notebooks.”

WiGig also benefit from the use of the unlicensed 60 GHz spectrum, says Mathias. The availability of greater bandwidth in that spectrum allows for faster transmission.

For now, the specification isn’t final. The Wireless Gigabit Alliance hopes to complete it by the end of the year.  From there it is up to companies to bring the technology to market.  WiGig will also have to battle other technologies to become the de facto standard.

“Ultimately, the question is how many different kind of radios do you really need?” says Mathias. “There’s not just competition from Wi-Fi and wireless HD but also cellular technologies such as 3G, LTE or WiMax.”

WiGig is likely to  bump up against IEEE’s attempts to introduce follow-ups to the 802.11g and 802.11n Wi-Fi standards. The IEEE (Institute of Electrical and Electronic Engineers), a non-profit organization, has been working on proposals to introduce the extremely high throughput 802.11ac and 802.11ad standards. The 802.11ad standard will also be based on the 60GHz spectrum but is not expected to be available before 2012.

“There are competing technologies to WiGig that are looking for standardization,” says Mathias. “The WiGig Alliance hopes to get a head start now and they might submit their standard to the 802.11ad group to be included in the specification.”

Either way this battle of the standards plays out, it is clear for consumers truly high-speed wireless data transfer is zipping into their living room.

Building wireless sensor networks

Tuesday, June 9th, 2009

Competitive pressures, globalization, rising energy prices, and increasingly stringent regulations are driving companies to cut costs while increasing efficiency and productivity. Industry leaders feel pressure to adopt new technologies that will help them gain competitive advantages wherever they can find them. One of these promising new technologies is wireless sensor networking. Wireless sensor networks (WSNs) dramatically reduce the cost of installing and commissioning instrumentation in industrial facilities. More instrumentation means better visibility into operational and environmental variables that affect overall uptime, safety, and compliance.

WSNs connect critical processes and assets with the systems or experts that can interpret the data or take immediate action. At the end of the day, operational teams with more visibility into their processes can prevent unplanned shutdowns, increase efficiency, and keep workers safe.

WSN is a term used to describe an emerging class of embedded communication products that provide redundant, fault-tolerant wireless connections between sensors, actuators and controllers or systems. WSNs provide access to assets or instruments that were previously deemed unreachable due to physical or economic barriers.

The WSN label typically describes products that provide performance above and beyond traditional point-to-point solutions, particularly in areas of fault tolerance, power consumption and installation cost.

Wireless Challenges While wireless provides clear cost and flexibility advantages, it also presents some challenges. Point-to-point radio communication links are notoriously variable and unpredictable.

A link that is strong today may be weak tomorrow due to environmental conditions, new obstacles, unanticipated interferers and myriad other factors. These factors can be boiled down into three major failure modes: interference, changes in the physical environment that block communication links, and loss of individual nodes.

RF interference: The small portion of the electromagnetic spectrum devoted to general-purpose wireless communication devices is crowded with traffic from Wi-Fi networks, cordless telephones, bar-code scanners, and innumerable other devices that can interfere with communications. Because there is no way to predict what interferers will be present in a facility at a given location, frequency, and time, a reliable network must be able to continually sidestep these interferers on an ongoing basis.

Blocked Paths: When a network is first deployed, wireless paths are established between devices based on the immediate RF environment and available neighbors. Unlike wired networks, these variables often change; paths may later be blocked by new equipment, repositioned partitions, delivery trucks, or very small changes in device position.

Assuring reliability for the life of the network, not just the first few weeks after installation, requires continually working around these blockages in a transparent, automatic fashion.

Node Loss: Node loss is an important issue to consider with wireless sensor networks. While node failure because of semiconductor or hardware malfunction is rare, nodes may be damaged, destroyed or removed during the life of the network.

Additionally, power surges, blackouts, or brownouts can cause nodes to fail unless they have an independent power source. End-to-end reliability requires the networking intelligence that routes around the loss of any single node.

Any of these problems will bring down a point-to-point wireless link. However, with a network architecture designed to protect against these issues, the network can isolate individual points of failure and eliminate or mitigate their impact, allowing the network as a whole to maintain very high end-to end reliability in spite of local failures.

Similarly, a well-designed wireless network architecture will transparently adapt to changing environments, allowing long-term operation with zero-touch maintenance.

WSNs aim to overcome these challenges by applying self-organizing and self-healing intelligence to continuously adapt to unpredictable conditions. The goal of WSN technology is to provide extremely high reliability and predictability for years at a time without constant tuning by wireless experts.

Time Synchronized Mesh Protocol (TSMP) provides a mechanism for WSN intelligence. By defining how a wireless node utilizes radio spectra, joins a network, establishes redundancy and communicates with neighbors, TSMP forms a solid foundation for WSN applications.

TSMP Overview TSMP is a media access and networking protocol that is designed specifically for low power, low-bandwidth reliable networking. Current TSMP implementations operate in the 2.4 GHz ISM band on IEEE 802.15.4 radios and in the 900 MHz ISM band on proprietary radios.

TSMP is a packet-based protocol where each transmission contains a single packet, and acknowledgements (ACKs) are generated when a packet has been received unaltered and complete. Mechanisms are in place to transport packets across a multi-hop network as efficiently and reliably as possible. All measures of reliability and efficiency are done on a per-packet basis.

Packet Structure TSMP packets consist of a header, a payload and a trailer. Packets contain fields that identify the sending node, define the destination, ensure secure message transfer and provide reliability and quality of service information. For the purposes of this article we will discuss the implementation of TSMP on IEEE 802.15.4 radios.

The IEEE 802.15.4 standard specifies a maximum packet size of 127 B, TSMP reserves 47 B for operation, which leaves 80 B for payload.

Time Synchronized Communication All node-to-node communication in a TSMP network is transacted in a specific time window. Commonly referred to as Time Division Multiple Access (TDMA), synchronized communication is a proven technique that provides reliable and efficient transport of wireless data.

Unlike wired systems where nodes can be directly connected by a dedicated wire (media), to the exclusion of neighbors, in a wireless system all devices within range of each other must share the same media. Several other Media Access Control (MAC) mechanisms are available including CSMA, CDMA and TDMA. TSMP is based on TDMA.

Timeslots and Frames In TSMP, each communication window is called a timeslot. A series of timeslots makes up a frame, which repeats for the life of network. Frame length is counted in slots and is a configurable parameter. In this way a particular refresh rate is established for the network.

A shorter frame length increases refresh rate, increasing effective bandwidth and increasing power consumption. Conversely, a longer frame length decreases refresh rate, thereby decreasing bandwidth and decreasing power consumption.

A TSMP node can participate in multiple frames at once allowing it to effectively have multiple refresh rates for different tasks. The concept of slots and frames is illustrated in Figure 1.


Figure 1. TSMP Timeslots and Frames.
Synchronization A critical component of any TDMA system is time synchronization. All nodes must share a common sense of time so that they know precisely when to talk, listen, or sleep. This is especially critical in power-constrained applications like WSNs where battery power is often the only option, and changing batteries can be costly and cumbersome.In contrast to beaconing strategies employed by other WSN implementations, TSMP does not begin each frame with a synchronization beacon. Beaconing strategies can require long listen windows which consume power.Instead, TSMP nodes maintain a precise sense of time, and exchange offset information with neighbors to ensure alignment. These offset values ride along in standard ACK messages and cost no extra power or overhead.A common sense of time enables many network virtues: bandwidth can be pre-allocated to ensure extremely reliable transmission and zero self-interference; transmitting nodes can effectively change frequencies on each transmission and the receiving node can keep in lock-step; bandwidth can be added and removed at will in a very predictable and methodical way to accommodate traffic spikes; and many others.

Duty Cycling It is important to note that TSMP nodes are only active in three states: 1) sending a message to a neighbor, 2) listening for a neighbor to talk, and 3) interfacing with an embedded sensor or processor.

For all other times the node is asleep and consuming very low power. In a wireless device the majority (generally >95%) of the total power budget is consumed by the radio, not the processor.

To achieve low power, it is clear that one must minimize radio on time. TDMA is very good at this. Timeslots are measured in milliseconds and in typical WSN applications this leads to a duty cycle of less than 1% for all nodes in the network (including those relaying messages for neighbors).

Because all nodes (including those often called .routers.) can be aggressively duty cycled, TDMA is the only practical solution for a fully battery-powered network.

In addition to slicing the wireless media across time, TSMP also slices it across frequency. This provides robust fault tolerance in the face of common RF interferers as well as providing a tremendous increase in effective bandwidth.

Commonly referred to as Frequency Hopping Spread Spectrum (FHSS), hopping across multiple frequencies is a proven way to sidestep interference and overcome RF challenges with agility rather than brute force.

Another technique to overcome RF challenges is Direct Sequence Spread Spectrum (DSSS). DSSS provides a few dB of coding gain and some improvement in multi-path fading. While beneficial, DSSS is not sufficient in the face of common interferers in the band, including Wi-Fi equipment, two-way radios or even Bluetooth (see figure 2 below).


Figure 2. Frequency Hopping vs. DSSS in 802.15.4 Networks.
It should be noted that a combination of FHSS and DSSS provides both interference rejection (FHSS) and the coding gain (DSSS).The other technique for overcoming interference is increasing the radio power, effectively turning up the volume. Although often effective, turning up the volume on IEEE 802.15.4 radios kills battery life and is not an ideal solution for low-power WSNs.Hopping Sequence Upon joining a network, a TSMP node (call it node C) will discover available neighbors and establish communication with at least two nodes already in the network, call them parent A and parent B (more on this in later sections).During this process node C will receive synchronization information and a frequency hopping sequence from both parent A and parent B. The IEEE 802.15.4 standard specifies 16 distinct frequency channels within the 2.4000-2.4835 MHz ISM band . so let’s use 16 as our number. The hopping sequence is a pseudo-random sequence of all available channels. For example the sequence may be: 4,15,9,7,13,2,16,8,1,etc.

Node C receives a distinct start point in the sequence from each parent, and when a new node joins it, it will in turn give a distinct start point to this new child node. In this way each pair-wise connection is ensured to be on a different channel during each timeslot enabling broad use of the available band in any one location.

In operation, each node-to-node transmission (say C to A) is on a different frequency than the previous transmission. And should a transmission be blocked, the next transmission will be to an alternate parent (C to B) on a different frequency. The result is simple but extremely resilient in the face of typical RF interferers.

Home automation network (HAN)

Thursday, June 4th, 2009

A basic overview of HAN architecture for AMI

The push for more consumer involvement in smart grid initiatives is slowly becoming more evident as companies and utilities attempt to grasp the overall impact of government mandated deployments of the smart meter. Understanding what the consumer needs and wants is quickly rising in importance with the goals and objectives of the energy industry.

There are various views and opinions as to how the US federal and state mandate translates to practical solutions. Primary as a viable solution is the deployment of smart meter technology. But not all smart meters are the same, hence the need for a more encompassing option. The complicated field of metering with its canopy of applicable hardware and software results in making intelligent decisions a difficult and rocky road for AMI proponents. Some have focused instead on defining what a smart meter is or isn’t. The resulting business models may or may not be implementable as technology changes the landscape or costly if human behavior fails to adjust to and embrace the deployed solution.

One thing is certain, that a smart meter without interaction from the occupants would diminish the gain in energy use reduction and jeopardize the utilities’ attempts at conservation and global warming compliance.

If the solution isn’t found through meter deployments, then it stands to reason that involving the consumer via technology and education makes sound business and good social sense.

This brings us to the need for a home automation network (HAN) – either a simple system or a complex one. Many envision the HAN with the smart meter as the center or focal point for data gathering and exchanging. The smart meter is the gateway through which the rest of the world garners information about the occupant’s electricity consumption. Others would rather have an independent gateway within the premise that is more controlled by the occupants with privileges allocated to the utilities or an AMI service company. The meter then would be just another peripheral device in the network that links the local network with the outside utilities. The internal home gateway would restrict and determine what information is available to external sources. The former is more in line with what the utilities are implementing while the latter favors the telecom, cable, and IT industry approach, which focuses on broadband home networks and less on low power mesh.

Planning a HAN in an uncertain market that is constantly changing and evolving can be daunting to any individual or company considering AMI deployments. Most seek simple solutions that require very little capital or are constrained to limited HAN implementation. Deploying programmable communicating thermostats (PCTs) is one way of semi-automating the home environment for demand response. Using in-home displays that link the external meter to a remote handheld or tabletop unit is another. Whatever the technology used, these early approaches to consumer involvement demonstrate a growing awareness for HAN planning and consideration.

Critical to planning any future HAN system is the communications architecture being considered. The current emphasis on mesh radio technology and the availability of completely different mesh protocols (ZigBee, Z-Wave, OpenRF, and so on) within each of these radio systems creates both opportunity and potential disaster when considering HAN development and deployment. Other networked communications architectures include power line modems, Ethernet, Wi-Fi, Bluetooth, and RS485 – all which add layers of complexity to deploying HAN technology. Coupled to this melee of competing options is the dearth of home networked products that provide meaningful and practical demand response solutions.

Making the right choice of communications backbone may well be defined in the legacy system requirements, the data requirements, the environment in which the HAN is located and how the HAN is to be used by the occupants. Cost and ease of deployment/implementation along with the level of after sales support required are considerations that impact a successful planned launch. Whatever choice is made, the decision to go with one or the other could also limit the availability of peripheral devices that can operate within that chosen communications architecture and by default the functions and features available to the consumer. So choosing wisely is paramount.

The correct solution to determining a HAN configuration is the “backwards” approach. Simply put, deciding what end result the network must accomplish and then determining which technology is best suited to do this. In most instances, a cost analysis report or a business case based on reliable information would suffice in evaluating the technology being considered. In other situations where the technology is not proven or the decision makers are not knowledgeable, a trial or test site may be necessary to familiarize everyone with the option.

As mentioned earlier, the market forces driving HAN development and deployment are directly related to the industry and its perspective of market need. Other drivers such as political and global issues also impact consumer anxiety and perception within the market. Hence developing a strategy for HAN architecture must take into consideration those drivers.

A typical HAN may consist of the following basic functional components:

  1. Node controller/gateway/central controller. A node controller is common within mesh networks for maintaining the communications link and exchanges necessary within the protocol. It may or may not be the gateway. The gateway, on the other hand, is the portal through which multiple conflicting protocols link and talk seamlessly. A central controller can be all three plus a data manger/data logger. It manages the network from a user perspective (such as a home computer or a home media server which can act as the controller).
  2. Peripheral devices. The fingers and hands of the HAN are seen in the sensor devices that gather information or provide levels of control. Such devices, such as a PCT, provide a measure of remote command and control to the premise HVAC system. Internal to these devices is the communications backbone which links the devices to the central element of the network.
  3. Software. There are myriad functions that must be accomplished for a HAN to successfully fulfill its intended design. For example, the mesh protocol software manages the mesh network communications within a low power radio configuration. At the gateway, the different protocols must be translated correctly and the data sent to the correct recipient. Throughout the network, some form of security must be employed – whether through software encryption or access denial methodologies. There is a large amount of embedded code within the peripherals that program the tasks associated with those devices. These command and control codes must be incorporated into a central controller which provides remote interaction with the sensing devices.

External to the HAN is the smart meter which may be the gateway to the utility. The smart meter may also just be a peripheral if the HAN has its own dedicated gateway. A smart meter that is very basic or uses wired access may need a HAN that incorporates a gateway. Shifting the gateway away from the meter may be a better cost solution or a strategic decision based on any number of factors. When deciding on the HAN to meter interfacing, these type decisions need to be considered.

HAN basic

A basic HAN (wired and/or wireless)