Passive electrical Components

802.15.4 and ZigBee RF4CE ultra low power system design solutions

Such as ultra-low energy ZigBee 802.15.4 wireless design and RF4CE Sensor networks

The new controller chip communication transmitter Architecture Design Centric

 

By Cees Links, CEO of GreenPeak www.greenpeak.com

 

The radio technology is further developed by the communication between humans and computers to facilitate communication between machines. There is a third wave of wireless, that after almost ubiquitous integration of cell phones and wireless Internet (Wi-Fi) in our lives.

The third wave consists of wireless sense and control wireless networks that connect and can control all types of aircraft in our homes and businesses – from the freezer to the light switch, the consumer electronics (TV, DVD player) and remote controls Sensors for detection or for the protection and fit locks and windows, central locking system in our homes (as we use in our cars).

Unfortunately, with today's wireless technologies, including most of the wireless sensor and control systems require the use of a large quantity of batteries to create environmental concerns (one thinks of toxic chemicals and heavy metals) and a serious maintenance problem (replacing the batteries continuously). Therefore, ultra-low power wireless networks, the very low power required are of great interest.

This includes systems that run on a single battery for the life of a device and network wireless sensors, energy recovery by (sometimes called energy scavenging) can be exploited. Create ultra-low power wireless networks and systems, can run the energy that is in the environment instead of batteries is a technology very promising.

 

Last year (the organization with several ZigBee of the largest consumer electronics worldwide (Panasonic, Philips, Sony and Samsung teamed up) to form what is called ZigBee RF4CE known radio-frequency for consumer electronics). This partnership between industry marks the development of a new generation remote controls – for TVs, home and office technology to communicate, many other types of remote control products for low-power RF instead of IR decades-old (infrared). By using this new communication technologies, we will soon see a wide range of devices remote not only interoperable between brands and models, but they require so little power, their batteries must never be changed or recharged. It is even possible to design and build remote controls without batteries will never get the power and energy recovery.

 

Challenges of wireless sensor networks

 

The biggest technical challenge for the development sensor networks, ultra low power is to manage energy consumption without affecting the Region, or functionality, such as speed and respect standards. The loss of batteries is to simplify maintenance and provide better user-friendliness and safety.

Very low

It is obvious that the current consumption – Milli-amp – the duty and cycling are important in sensor networks without wire. However, minimizing energy consumption is only part of the solution. There are some essential questions to develop key applications of low power wireless sensor, but it all starts with the development of chips with ultra low power radio transmitter and receiver.

Thanks to a communication controller chip design centered instead of a microcontroller-centric design, with synchronized wake-ups, it is possible to reduce the total electricity consumption by 65% ​​or more.

Most solutions require the transceiver the MCU can be switched on all the time while transmitting a packet. Through the use of technology GreenPeak GP500 communication controller, the MCU only necessary to transmit or receive data processing.

Most low-power radio networks on a micro processor approach to manage all the necessary information to the transceiver. This requires the microcontroller to be awake all the time, which in turn requires extra energy. Using an approach to energy-efficient communications controller and the transceiver can send and receive data independently of the microprocessor and the microprocessor to wake up and used if necessary to continue to treat data.

By having a hardware-based scheduler and the synchronizer in the chip itself, to see the radio wakes up only when necessary, if there are data that is sent. Otherwise, it returns to sleep. If it passes the data must be, the controller wakes up the microcontroller. The chip then sends the information and then goes back, he had planned to wake up the next time, sleep. There is no message to be sent and the controller should not revive the microprocessor – 9999 of 10000 times. Each time data is sent to a message transfer tokens to ensure synchronization we all wake up together the next cycle.

By choosing the communication controller, when they wake up and check the messages, it is possible to reduce overall energy consumption much more. Because the planner and synchronizer communications controller, the system wakes up only for a brief moment to see if new and goes back to sleep. by the microprocessor to sleep until it is needed, it is possible more than 65% of energy consumption, except for a typical transceiver always compared to conventional

If you multiply the individual node power saving mode by a wireless network with over 100 nodes, it is clear that all network to be able to work with much less energy than a conventional microprocessor system.

Peak energy savings

There are three types of wireless sensor nodes States a platform for wireless sensor commonly used. Everyone has their own level of energy consumption. In a statement, the microprocessor and the transceiver in sleep mode (10μA). In Two state, the microprocessor is asleep when the transmitter (10 mA) is enabled. In condition three times the transmitter and the microprocessor are awake (27 mA).

When closely examining the behavior of power consumption electronic circuits, it becomes clear that this which is the beginning of a current plane curve actually bears more resemblance to a mountain range with mountains and valleys. When certain functional blocks are active, they draw peak current. When two functional blocks move simultaneously, doubling amplitude.

The secret of reducing peak power lies in the careful management of on and off of the most important functions, so that double peaks can be avoided.

Synchronized Wake Up Sleeping and allows the reduction of electricity consumption for the low-power mesh networks

One of the differences most marked between the sensor technology of wireless communication and other wireless technologies known is the ability of sensor nodes to send messages from other nodes further down the chain of communication in the lead. This technique, known as the network multi-hop routing and networks provide an efficient and reliable large-scale infrastructure covering the whole range of what a wireless connection can achieve alone.

For a node receive a message from another node before it is awake and in a receive mode, if the initial wireless message arrives. Unfortunately, reception requires much more power than the batteries it running in a matter of days. How can that life is too short for most practical applications, the simplest solution, as defined by accepted industry standards, is the ability to multi-hop nodes that are permanently connected to the limit Food. In this context, Low power devices, which means that in a power mode down, mostly, are not able to relay messages to other devices. This low power devices such as end equipment are known, at the end or the beginning the chain of communication.

This framework, the mesh network operation and routing equipment Low power end devices combined works for some applications. Take, for example, a desktop application using a wireless lighting LEDs connected and switches. The lamps, which are among the most important source of power, House of nodes of the mesh connected routing communication. Switches not the operation of the network, a natural place for the end equipment.

Many other applications do not adapt not well within this framework. In applications such as gas detection, fire detection, access control, surveillance of the field of precision agriculture perimeter surveillance, monitoring of storage temperature, etc., is available voltage is not readily available or even present. Perform a power cable in these applications would be too expensive, offsetting the benefits of wireless communications.

For this class of applications requires low power multi-hop networks, or low-power routing, in which all nodes to operate, including the mesh nodes, routing low-power mode.

Using a "synchronized clock" scheme, it is possible to coordinate the activities of maintaining a way that the need for routing mesh nodes that operate continuously in receive mode, which significantly reduce power consumption. The image below shows how the routing of low power, when node A wants to send a message to node C through node B. All nodes in the images are low power nodes, sleeping most of the time worked.

By synchronizing the sleep / wake cycles of nodes to each other, wake-node if receives a message waiting for an adjacent node. This enables routing nodes in operation, an almost helpless dormant most of the time, making an ultra-low power. Clear that there are more awakenings than is absolutely necessary for the transport of data, such as neighboring nodes are not always data to be transmitted. But the extra power for periodic wake-ups and synchronization is required that power by the need to constantly stored offset mode operation.

Since its inception, the technology of wireless sensor with electronics low power were combined. Most low-power wireless sensor networks have been designed for low power which means they consume little energy when turned on. This is not enough. Through the use of communication chips focused on the transceiver, Wireless mesh networks and synchronized sleep and waking cycles, developers have set up systems that do not even need batteries and can, in rather than energy harvesting power of the sensor network environment from power sources to use.

The wireless sensor network standard – IEEE 802.15.4

 

For transceivers wireless sensors, the dominant and probably only real standard is the IEEE 802.15.4 specification. However, there have been efforts, Bluetooth and Wi-Fi applications low power sensors. Used in most reported cases, Bluetooth and Wi-Fi in a non-standard, in reality, weaving the principles of implementation IEEE 802.15.4 in their native language. It is now generally accepted that IEEE 802.15.4 offers the best basis for wireless applications in sensor network.

In addition to IEEE 802.15.4, to have a number of technology vendors to build proprietary transceivers. The main motivation seems to be a reduction of complexity and therefore lower cost potential. See It remains to see if a proprietary solution will never reach sufficient volumes to be achieved effectively, the weak theoretical cost. Moreover, the complexity is reduced automatically goes conjunction with the sacrificing performance and applicability.

Proprietary technologies are vulnerable for two reasons: (1) owner of the technology that controls the specification and therefore the price, and (2) The customer is dependent on proprietary technology updates, and continue sourcing.

Even within the standard technology provider can discover and use the possibilities of differentiation.

As an example GreenPeak has an emitter cell technology and the network, which is consistent with the IEEE developed 802.15.4/2.4 GHz standard, however, include other features that allow its use for ultra-low power applications. Applied ultra-low consumption as an application that is able to live a button cell is defined and energy from the environment through a solar cell, a vibrational energy harvester or other energy harvesting transducers room.

About the Author

Cees Links is CEO and founder of GreenPeak Technologies, based in Utrecht, The Netherlands. Cees ["case"] Links is a pioneer of the wireless data industry, a visionary leader bringing the world of mobile computing and continuous networking together. Under his guidance, the first wireless LANs were developed which ultimately became house-hold technology integrated into the PCs and notebooks we are all familiar with. He also pioneered the development of access points, home networking routers and hotspot base stations, all widely used today.

He  was involved in establishing the IEEE 802.11 standard, the Wi-Fi Alliance, and IEEE 802.15 standardization committee.