Wireless Protocols

Title: Wireless Protocols

Introduction

This document is a high level view of few prevalent wireless technologies.

The aim is to create a perspective about technology that we popularly refer to as wireless – in these cases devices communicate in isolation or as part of a larger, more complex network.

The following information is provided in the comparison table below:

Comment

A small comment on the technology.

Protocols

There are a large number of protocols.  This can be very confusing to the beginner. The protocols mentioned here are popular and indicative ones for that technology – not an exhaustive list. This value is provided here only for information, just to help make the association, and as a pointer to further details to help understand what they do with respect to addressing, handshaking, data transmission, encoding; point to point or broadcast; node/ instrument profile as transmitter, receiver, repeater, master, slave, etc.

Very often the protocols that these technologies are referred to by are the low level protocols (Layers 1 & 2 as per OSI model).

For example:

  • The 802.* series.
  • Phone manufacturers that support WiFi will say that they support IEEE 802.11 a/b/g/n

Frequency

Is provided for information purposes only. The frequency range gives an idea about the transmission characteristics.

The characteristics vary widely across different spectrum bands. There is no definite trend, and each one is different.

For example, low frequencies ( long wave)may travel longer distances since they are reflected by the earth and the atmosphere.

Frequencies in the optical range have their own unique properties. Very high frequencies have good penetration, and can pass through barriers like walls, for example.

Other generalizations, not wholly accurate, are that at higher frequencies more data can be transferred, as compared to lower frequencies. Also higher frequencies consume more energy (in part due to the absorption characteristics of the media)

A popular classification is of the kind to ULF, VLF, VHF, EHF, etc.

http://en.wikipedia.org/wiki/Radio_spectrum#By_frequency

Range

In case of wireless communication, the range that can be covered depends upon the power available. Frequency bands to transmit information are an important and precious resource, and this controlled by a regulatory body.

All the technologies that we look at here operate locally (except mobile technologies) over small distances, and come under the ISM (Industrial, Scientific and Medical) band. ISM operates at 868 MHz in Europe, 915 MHz in the USA and Australia and 2.4 GHz in most jurisdictions worldwide. Data transmission rates vary from 20 kilobits/second in the 868 MHz frequency band to 250 kilobits/second in the 2.4 GHz frequency band.This band allows people/devices to communicate locally wirelessly. The regulation controls the range over which the devices can transmit.It does so by limiting/specifying the power rating.

The value here gives an idea of usual ranges in domestic applications.  Like between point to point communication. Or between a transmitter and a receiver. As opposed to between nodes in a network.

OSI Layer Level

It helps when designing your application to think about the OSI Layer Level. This allows to cleanly consider the modules and stack the interfaces.

It’s a large topic.

A popular schematic to depict the OSI model is:

THE 7 LAYERS OF OSI
Transmit Sender Receiver Receive
Application LAYER 7 Application
Presentation LAYER 6 Presentation
Session LAYER 5 Session
Transport LAYER 4 Transport
Network LAYER 3 Network
Data link LAYER 2 Data link
Physical LAYER 1 Physical

The 7 layers can be split logically into two subgroups.  The upper layers focus on the end to end communication of data source and destinations.  The lower layers focus on consistent communication between the network devices.  The upper layers deal with application issues and are implemented only in software.  The highest layer, the application layer, is the closest to the end user.  The lower layers are responsible for the transportation of the data.  The physical layer and the data link layer are implemented in hardware and software. The lowest layer, the physical layer, is closest to the physical network medium (the wires, for example) and is responsible for placing data on the medium.

e.g –

  • In case of the popular TCP/IP protocols:

TCP is a Layer 4 Protocol. Transport layer

IP is a Layer 3 Protocol. Network layer

  • VOIP layers are described as  (from vvfvoip.pdf from cisco – mentioned in References) :

OSI Layer Number     OSI Layer Name     VoIP Protocols and Functions

7             Application         NetMeeting/Applications

6             Presentation         Codecs

5            Session         H.323/MGCP/SIP

4             Transport        RTP/TCP/UDP

3             Network         IP

2             Data Link         Frame Relay, ATM, Ethernet, PPP, MLP, and  more

  • HTTP is at Layer 7
  • Data cables are at Layer 1
  • Electrical pulses are at Layer 2

We will roughly use this OSI model for our understanding since all layers may not be applicable in every scenario.

Most wireless technologies are at the very least data networking protocols layered on top of a radio signal. This may extend all the way to end user applications.

e.g.- GPS protocols are wireless protocols in that sense, but are not generic communication protocols like the ones we inspect here.

Comparison Table

Technology Name Comment Protocols(for example) Frequency (indicative)Range/Energy OSI LayerLevel Sample Applications
Wifi Used for Ethernet compatible wireless connectivity. IEEE 802.11 a/b/g/n(at OSI levels 1 & 2) Short wave radio transmission in ISM and 5/5.8 GHz bands50 m indoorsUpto 100 m outdoors

(Without signal enhancers, which can spread it over kms)

Layer 1 /2After that it implements Ethernet protocol stack All Ethernet/ Internet applications
Bluetooth Originally conceived as a wireless alternative to RS-232 data cables. It can connect several devices, overcoming problems of synchronization.A plus is that Bluetooth profiles are built into very many devices.A minus is that cross vendor command set standard is not well in place. http://en.wikipedia.org/wiki/Bluetooth_protocolsOriginally standardized as IEEE 802.15.1, but standard is no longer maintained by IEEE Short wave radio transmission in ISM bandClass 1: range up to 100 meters (in most cases 20-30 meters)Class 2: range up to 30 meters (in most cases 5-10 meters) Layers 1-7Designed and referred to end-to-end Bluetooth profiles come built into wireless devices like keyboards, mice, headsets, etc.http://en.wikipedia.org/wiki/Bluetooth_profilee.g. – Some commonly available profiles in mobile handsets are

(AVRCP 1.0, GAP, A2DP 1.2, HSP 1.1, PMP, HFP 1.6, HIDP 1.1, MAP, HDP 1.1, OPP 1.1, PANP 1.0, PAP 1.0).

Please check on internet

Zigbee Designed to be used in low-cost, low-power wireless sensor and control networks.Can be used to create a mesh network IEEE 802.15.4(at OSI levels 1 & 2) Short wave radio transmission in ISM bandUpto 100 metersDesigned to go dormant when not invoked actively and thus consumes very little power http://www.sensor-networks.org/?page=0823123150 Zigbee Alliance with over 70 vendors have created products that cater to one of several Zigbee profiles/standards such as:Zigbee Building AutomationZigbee Health Care

Zigbee Input Devices

Zigbee Light Link

Zigbee Network Devices

Zigbee Smart Energy

Zigbee Telecom Services

Refer to http://www.zigbee.org/Products/ByStandard/Overview.aspx

IR Mostly used in remote controls to wirelessly control devices.Is directional, usually line-of-sightUses phototransistors, infrared LEDs.

Very inexpensive.

Widely available as emitter, receiver pairs.

www.epanorama.net/links/irremote.htmlMostly proprietary protocols from vendors.e.g. – RC-5, SIRCS Infrared is the spectrum referred to between the radio spectrum and the optical spectrum.i.e. – from approx. 300GHz to 430THz.The IR LED is pulsed in the range of 38-40kHZ. So that is the operating frequency.

Thus used for low bandwidth data transmission.

Upto 10 m

Very low power

Layers 1-7Designed and referred to end-to-end Used in all kinds of remote controls.For TVs, music systems, RC toys, etc.
Mobile This needs to be considered as it is the most important wireless network.Very vast, ubiquitous, heavily used network.Is a precisely regulated area, since there is a lot at stake here.

Is also very important for us to note the integration between internet and telephony networks.

The large telephony infrastructure/network available can now be used to access the internet and its wide range of services

Very many protocols are in use. For a list of some cellular protocols, see here.http://www.protocols.com/pbook/cellular.htmSome popular nomenclature is:

2G, 3G, 4G

GSM (or CDMA) is 2G

GSM + GPRS is 2.5G

2.5G + EDGE is 2.75G

UMTS is 3G

Please check on internet

GSM – 850, 900, 1800, 1900 MHzUMTS – 2100 MHz Layers 1-7 when we consider voice applications.Layers 1-4 when we consider non-voice Internet Apps accessed over mobile networks VOIP applications(See the profile of a vendor like Twilio)All Ethernet/Internet applications, as the distinction between an Ethernet network and a mobile network is blurring.
RFID Classified as Active and Passive systems based on whether the tags are powered or not.Since it has a wide range of applications, the costs of the RFID setup can vary widely. e.g. – ISO 15693, ISO 14443, ISO 14443-A, EM4001 Common frequencies are:Low bands : 125 & 134.2 kHzHigh bands: 13.56 MHz (this one allows for faster read rates and longer range reads)

Range is typically from few inches to few feet.

Layers 1-7 Innovative solutions for tracking all kinds of inventory including tags/systems designed for tracking livestock.

Another Comparison

An interesting comparison between ZigBee, Wi-Fi and Bluetooth (These 3 technologies operate in the same frequency bands and similar ranges. GSM does not quite fit in this bucket).

From http://www.zigbee.org/About/FAQ.aspx#17

How does ZigBee compare to other wireless standards?

Zigbee OSI model

(as an example)

From http://www.sensor-networks.org/?page=0823123150

Pros and Cons of Wired vs. Wireless

  • Obviously the big and overwhelming pro for wireless is mobility.
  • It comes in handy where there is little infrastructure
  • In wired communications, losses are less, errors are fewer, data transfer capacity is much higher, power consumed is less, since data is directional.
  • Wireless devices need a source of power, like a cell.
  • In wireless, the signals have to contend with more noise.
  • In wireless, the equipment – transceivers, modems, etc. are comparatively more expensive.
  • Data carrying capacity is obviously higher in wired than in wireless.

References / Further reading:

http://en.wikipedia.org/wiki/Radio_spectrum

http://electronics.stackexchange.com/questions/33537/why-do-higher-frequency-waves-have-better-penetration

http://en.wikipedia.org/wiki/Wi-Fi

http://compnetworking.about.com/cs/wirelessproducts/f/wifirange.htm

https://supportforums.cisco.com/thread/2209755

http://www.cisco.com/en/US/docs/ios/12_2/voice/configuration/guide/vvfvoip.pdf

http://www.sis.pitt.edu/~icucart/networking_basics/7layersofOSI.htm

http://www.tutorialspoint.com/gsm/gsm_specification.htm

http://www.radio-electronics.com/info/wireless/wi-fi/80211-channels-number-frequencies-bandwidth.php

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