IEEE 802.15.4e Standard

Low reliability, unbounded packet delays and no protection against interference and fading are among the limitations of the IEEE 802.15.4 standard, which prevent its adoption in applications with stringent reliability and latency requirements. Reliability and timeliness are critical issues for healthcare and industrial applications. If data packets are not delivered correctly and within a pre-defined deadline, the correct behavior of the system may be compromised.

IEEE's 802.15.4e amendment introduces enhancements and modifications to the MAC layer of IEEE 802.15.4 in order to overcome these limitations. It improves the old standard by introducing mechanisms such as time slotted access, multichannel communication and channel hopping . It defines five new MAC protocols (called MAC behavior modes) to support specific application domains and some general functional enhancements that are not designed for specific applications.

Functional Enhancements

The following enhancements were introduced in the 802.15.4e standard:

1. Low Energy (LE) for applications that can trade latency for energy efficiency. It allows a node to operate with a very low duty cycle (1% or below) while appearing to be always on to the upper layers. This enables the IoT paradigm, which uses Internet protocols that assume that hosts are always on.
2. Information Elements (IE) are an extensible mechanism to exchange information at the MAC sublayer.
3. Enhanced Beacons (EB) are an extension of the 802.15.4 beacon frames and is more flexible. It allows the creation of application-specific frames by including relevant IEs.
4. Multipurpose frame provides a flexible frame format that addresses a number of MAC operations. It is based on IEs.
5. MAC Performance Metric is a mechanism to provide feedback on the channel quality to the network and upper layers, so that appropriate decision can be taken, e.g., the IP protocol may implement dynamic fragmentation of datagrams depending on the channel conditions.
6. Fast Association (FastA). The 802.15.4 association procedure introduces a significant delay in order to save energy. For time critical applications, reducing latency is more important than energy efficiency. The FastA mechanism allows a node to associate in a shorter time.

Message Queuing Telemetry Transport for Sensors (MQTT-S)

WSN is integrated with the traditional wired network because many WSN applications involve transferring data collected by sensors to a traditional wired network (e.g., LAN, Internet). The WSN consists of many sensor-actuator (SA) devices with limited amount of storage and processing capabilities that collect information from their environment. The collected data is sent to the gateways and transferred to the applications.

The network is very dynamic (e.g.., devices may fail, wireless links are more likely to fail). Some protocols (e.g., ZigBee) change the device address from time to time. Consequently, it is not practical to use network addresses for SA devices and applications to communicate. It is not uncommon for an application to not know the address or identity of the devices that deliver the information it requires. The application is only interested in the data content.

Integrated WSN and Traditional Network

IEEE 802.15.6 Standard

A wireless body area network (WBAN) connects independent nodes that are placed in the clothes, on the body or under the skin of a person. The network expands over the whole human body and the nodes are connected through a wireless communication channel.

The IEEE 802.15.6 Standard defines a communication standard optimized for miniaturised low-power devices that are deployed on or implanted inside a human body for a variety of medical, non-medical and entertainment applications.

In medical application, WBAN allows remote health monitoring of a patient over periods of time without any restriction to his activities. Vital information of a patient is collected and continually forwarded to a remote monitoring station for further analysis. WBAN can also be used to help people with disability.

Non-medical applications include monitoring forgotten things, data file transfer, gaming and social networking.

Mobile Ad Hoc Network (MANET)

An infrastructure-based network, such as a cellular network, uses fixed BS that are responsible for coordinating communications between mobile nodes. An ad hoc network consists of mobile nodes that communicate with each other using wireless medium without any fixed infrastructure. “Ad hoc” is a Latin word that means “for this purpose only”. An ad hoc network is a special network that is set up for a particular application.

A mobile ad hoc network (MANET) is a self-configuring network of mobile routers connected by wireless links that form an arbitrary topology. The routers are free to move randomly and organize themselves arbitrarily. The network’s wireless topology may change rapidly and unpredictably.

Why Use MANET?

• Ease of deployment,
• Speed of deployment,
• Flexible,
• Decreased dependence on infrastructure,
• Cost effective,
• Interoperability.

Characteristics:

• Decentralized,
• Self-organised,
• Self-deployed,
• Dynamic network topology,
• Bandwidth-constrained, variable capacity, asymmetric links.

Mobile App Development: What's Different?

In many ways, developing mobile apps is similar to software engineering for other embedded apps. However, there are additional requirements that are less commonly found with traditional software applications.

1. Potential interaction with other applications — Most embedded devices only have factory-installed software, but mobile devices may have numerous applications from varied sources with the possibility of interactions among them.
2. Sensor handling — Most smartphones include an accelerometer that responds to device movement, a touch screen that responds to gestures, real and/or virtual keyboards, GPS, a microphone usable by applications other than voice call, camera and multiple networking protocols.
3. Native and hybrid (mobile web) applications — Most embedded devices use only software installed directly on the device, but mobile devices often include applications that invoke service over the telephone network or the Internet via a web browser and affect data and displays on the device.