The Ultra High Speed Wireless Communication

Published Date: 02 Nov 2017

INTRODUCTION:

21st century tremendous demand for digital Multimedia content to be available at break neck speeds in every growing wireless environment and be available to users having portable handheld devices and smartphones has created a new problem under wireless communication .Digital media as we know consists of highly uncompressed content typical at high bitrate. These are high definition format (HD) media , peripheral docking and display as they require much higher bandwith. The Current commercial product can provide limited wireless transmission under standard conditions whereas Wireless docking and display as well as Gigabit network access needs a new standard rather than current Wi-Fi technology because they require much high data transmission .Current state of Wi-Fi is being converged with Gigabit communication so that devices across all ranges are able to reap benefits of Gigabit communication. This has given rise to new Wireless Gigabit communication under WiGig Alliance[1] - a consortium unified under a specification for wireless communication which is designed to drive a new ecosystem for interoperable products .WiGig alliance will provide a way by which many devices will access network at Gigabit speeds and also development in 60GHz band which is being deployed by WiGig alliance within MAC and PHY layers will facilitate new era of wireless access as well will be forefront of emerging standard in near future as per IEEE new 802.11 amendment. Development of medium access (MAC), physical (PHY) and several protocol adaption layers (PAL) layers in to specification will provide a way by which extremely high data rates can be achieved .The main objective in this paper will be to address the specification put forward by WiGig in accordance to new 802.11 standard as it will supersede 802.11n standard currently in use today . Then in next section we look upon 60GHz signal analyzing its properties and why it will be a successful candidate for Gigabit communication and further examine and investigate the challenges faced during the implementation by 60GHZ band into Wireless personal area network. The last section looks at the real world applications whereby this new technology will be placed in future.

Specification of Wireless Gigabit as per IEEE

Wireless Gigabit technology will be supporting transmission speeds up to 7 Gbps which is 10 times more the 802.11n operating upon unlicensed 60GHZ frequency band which is multi-channel spectrum. The reason for using 60 GHz is the availability of spectrum having four wider channels of 2.16GHz. These wider channels in WiGig specification enable it to support application that require extremely fast transmission rates such as for uncompressed video transmission. WiGig has designed Wireless gigabit model ground up for low power devices such as smartphones .High performance computer which supports WiGig technology will have advanced power management system to minimize power loss and built in security. As it is based on IEEE 802.11ad specification ,so it will transparently switches for native Wi-fi band frequency operating on 802.11 networks .WiGig specification put forward is as same as IEEE 802.11 a/b/g/n of MAC and PHY layer but having added features to improve performance over 60GHZ band .One new aspect in WiGig specification is that of beamformaing protocol in which devices with directional antennas discover each other to establish connection and once connection is made refinements to antenna setting are made to maximize transmission and receiving gains to data rates which will be explained later in the paper.

Gigabit wireless has a tri-band architecture having medium access MAC and physical PHY layers specification directly implemented in hardware so that IP networking is achieved over 60 GHZ band .The devices are simpler and less expensive to produce so that they can communicate over all three bands 2.5GHZ ,5GHz,and 60GHZ.Protocol adaption layer is yet another layer in which support for audio/visual and input /Output display standard is provided . Connectivity options such as HDMI,display port as well as USB /PCIe defined in PAL so as to support docking .[1]

Physical (PHY) layer has unlicensed 60GHZ band which has much more spectrum available because the spectrum is divided in multiple channels Modulation and coding schemes included are Orthogonal frequency division multiplexing (OFDM) so that signals travel over long distances and have greater delay spreads. Due to OFDM signal will be flexible in handling obstacles thus achieving transmission desired speed upto 7 GBps The extension of Single carrier (SC) mode in WiGig will support 4.05GB/s speeds so that low power devices are supported. To promote interoperability OFDM and SC modes will share a common preamble and channel coding to reduced implementation complexity .Coding rates employed in PHY layer are of order 1/2,5/8,3/4 and 13/16 as all of these are low density parity check codes on both OFDM and SC modes .As fading condition is encountered the wide range of these codes are employed by transceiver so that best code rate are chosen as they are specifically designed for implementation and have property such as layer decoding and full parallel belief propagation decoding. From security point of view PHY layer in WiGig incudes advanced encryption standard in Galious-counter mode requiring fewer computation per block as that of AES in 802.11.For efficient data transfer rates, packet aggregation and block acknowledgement mechanism is present to achieve efficient data transfer rates [1]

MAC Specification enables cable replacement and provides many features such as power management support for advance usage models and its integrating in exiting Wi-Fi networks.as it has the ability to switch seamlessly between 60GHz and 2.4 GHz and 5GHz within MAC . Hence if mobile device moves out of range of 60GHz thereby quickly fall back to low rate connection so seamlessly network connectivity is maintained within devices .Power management is based upon scheduled access method so that devices goes in sleep mode when it not using the network to save power . Battery power devices such as mobile phones will especially benefit from it all because it may allow the devices to specifically tailor their power needs as per requirements. Extension as well as supplication for 802.11MAC layer with backward compatibility towards 802.11 n MAC is provided in WiGig . Point to point communication between two wireless devices and network is incorporated in MAC layer as such.

PAL’s (Protocol adaption layer) is one such feature implemented in hardware of upcoming devices which will support gigabit technology. PAL will provide with a solution by which implementers to produce devices that will provide usage models so that wireless display and HDMI connection in which without the need of wires is supported. HDCP which is protection of digital content when it is transmitter through the interfaces is also included in the specification. Input output connectivity which includes USB and PCIe so that it will allow docking mechanism as such peripheral devices can connect without the need for wires .As well as for CPU,storage and other I/O related operation, PAL will provide necessary multi gigabit synchronization at a very high speed. It will negotiate as a peripheral connector by which CPU and other storage related operation are handled within a system .Main goal of PAL will be to facility high speed gigabit communication for offline and online processing. PAL layer as per WiGig specification sits in the middle of 60GHz PHY/MAC and a bus or display interface acting as a interface between them. This provides a functionality is in contrast to Typical IP networking in which additional IP stacks sit over MAC. PAL simultaneous operation in two modes is yet another feature incorporated as such a device using WiGig 60GHz MAC/PHY can carry steaming media over PAL as well as over IP stack .

WiGig has also new technique called Adaptive Beam forming protocol As 60GHz suffers from propagation loss much more than 2.5GHz and 5 GHz band so to enable robust gigabit communication at distances beyond 10meters directional antenna focus a concentrated beam between two devices . So during this process as devices establish connection and they also fine tune their antenna setting as to improve the signal so that there is enough spectrum capacity for desired data transmission is achieved . Another feature in beamfomaing is that if a object or a person comes between two devices ,the protocol establish a communication pathways such that beams bounce off the walls so that connectivity is maintained.

60GHZ Solution and Why its will be successful :

Attractive features of unlicensed 60GHz band also know as Millimeter band(mmWave in short) as it lies within range of 57-66Ghz is that of the abundance of spectrum due to which 60GHz proves as big plus point in terms of spectrum analysis as compared to already exiting low frequency bands in current Wi-Fi infrastructure.

Properties of 60GHz such as free space propagation loss and Quasi optical meaning strongest components should be in line of sight(LOS) [] .Free space propagation loss can be compensate by using high gain directional antenna .As far as Line of sight operation is concerned require two devices to be in range with each other as 60GHz signal is of short wavelength ,it imposes a serious challenges such as diffusion and diffracting around obstacle’s .So implementation of 60GHz in indoor environment is limited by penetration loss more than free space propagation. Link characteristics as compared to low frequency bands 2.4/5GHzis much less as compared to 60GHz as so here is a huge diversity in multipath and ranges to hundred kilometers.

Another question arises is that how will 60GHz converge with WLAN and WPAN environment. In [] WPA and WLAN are differentiated with regard to traffic pattern as it has been pointed out that other than traffic pattern in WLA topology and how they route traffic is clearly the same as compared to WPAN i.e there data rates,datatypes power requirement ,range )all are the same .Usage models of WPAN with 60GHz include Sync n go ,Wireless docking and Wireless display all requiring Gigabit per second data rates .

Unification of both 60GHz\ and lower frequency band under a single band is being looked upon .Since 802.11 is already being drafted by IEEE [] to improve its performance in ad hoc mode first then to mesh networking thus making it more friendly to peer to peer usage.Futher improvement to 802.11 such as emergence of 11s promises a single hop ad multi hop based peer to peer usage for WiFi devices .

60 GHz on the other hand might provide a opportunity if it is reinforced so that performance of WLAN and WPAN reach gigabit level. Some of real world challenges to 60 GHz exits which include interference from world objects suchs as furniture and people walking around in between devise and particular with a office environment.WiFi in particularly prove to be better in indoor environment regarding range and NLOS channels due to rich scatters.

So to address the needs of WLAN and WPAN, Multi band radio devices may begin to emerge . In these devices, whenever a outage of 60Ghz occurs device will switch back to lower frequency band thus maintaining network connectivity.

Research in MIMO (Multiple input multiple out) [] in 802.11n is currently ongoing. Spatial multiplexing within MIMO will prove to have a huge boost in terms of performance to 802.11n as the number of antenna packed are in small form factor typically at a reasonable cost of installation would be possible but current commercial products in market today do not use more than 3 antennas In near future to achieve high data rates in 2.5 GHz and 5Ghz band, one way is to increase the channel bandwidth beyond 40GHz .Since MAC throughput increases with overheard in channel capacity at a faster rate so as such MAC throughput does not scale well with PHY data rate .Analysis in MAC efficiency [][] has proven that to reach 1Gbps transmission, PHY layer rate has to be in 3 ms transmission opportunity (TXOP) requiring at least 2.4GHz of channel bandwidth. Reason why 60Ghz band is effective is show by ECMA[] and 15.3[] drafts as channels of 2.16 are divided in 60Ghz so wider channels enable high data rates .Draft put forward by 15.c shows again if modulation techniques such as QPSK(Quadrate phase shift keying )or 16-QAM( Quadrate amplitude modulation ) are carried out single carrier in PHY layer thus achieving data rate of 2.664 GBPS and 4.965Gbps respectively. In [] it has been pointed out that use of ultra wide band(528Mhz) is also not adequate for Gigabit rates because the EIRP (Equailent Isotropically Radiated power ) as per FCC regulation cannot exceed -41.3 dBm .Comparing it with 60 GHz it EIRP is over 40dBm).So performance is limited in Ultra wide Band as compared to 60GHz.

Advances in CMOS technology to build in expensive and low power transceiver is being done. Some of properties of 60GHz channel such as free space propagation loss can be compensated by using directional antenna as to achieve decent range .Another property which 60GHz exhibits is that strongest components must be in Line of sight but Non line of sight components also mostly exhibit as reflection .Sector antenna and adaptive antenna are being used in arrays to achieve shorter wavelengths of about 5mm by having different radiation patterns

Challenges, Motivation and implementation of Wireless gigabit technology (60GHz) in Wireless Personal area networks:

Integration of Gigabit technology in Personal area network is one interesting area to be looked upon. Investigating and implementation of Wireless personal area network with 60 GHz has highlighted few challenges in wireless infrastructure 60GHz unlicensed spectrum is thus a solution to short range wireless networking.Figrue shows the current available spectrum worldwide .Europe already has 59-66GHz of mobile broadband whereas USA and Japan are behind with 56-64GHz ,59-66GHz of unlicensed application .The attenuation in 60GHZ signal is one such property with concrete wall and other material has been examined in [2] Small room and conference halls are thus well suited for 60GHz transmission. Localization of signal proves to a positive impact on security due to beam width which in this case is narrow because of presence of directive antenna operating at these frequencies. The required equipment for interfering with these is very expensive and not readily available. To make spectrum much more attractive, exploitation of attuetation in 60GHz signal for frequency reuse by isolation of nearby transmitters can form a excellent base for wireless Networking.

In [2] it has been explained that Wireless personal area networks are long haul backbone networks used as extension for wired fiber optic networks operating point to point using large directional antenna array so that as Operational ranges from 60GHz signal exceeds 1km of area with speeds upto 1.25Gbps.In [2] it has also been shown why motivation of these network is feasible .In [2] Wireless area networks are defined as short range network as 10m usually put in place for personal use such as in small room or conference halls . In [2] challenges into when wireless personal area network are integrated with Gigabit personal network 60GHz technology is shown to highlighting problems of transmission power due to path loss is present as Fiirs equation to compute this effect clearly show. All because 60 GHz signal suffers from a loss of power much more as compared to 2.5GHz and 5GHz band all because of short wavelength but can be compensated for increasing antenna gains .Solution to this problem is given in [2] that if we use small antenna loss in transmission power is much more less as 60GHz for the given antenna gain scales inversely with square of wavelength. Doppler spread due to motion of terminal ,channel blockage present due to Non line of sight ,Multi path fading environment and last but not least Network infrastructure because of need to generate and handle large amount of traffic are some of concerns in wireless personal area networks are examined as well in [2]

Conclusion

We have shown the specification currently in place for Wireless Gigabit communication with regard to IEEE’s new standard being developed in collaboration with Wireless gigabit alliance . They are leveraging the state of art millimeter technology so that widespread use of 60 GHz band is put in place in near future .Wireless docking, wireless display as well as Sync on go are some of important milestones in terms of applications are to be accomplished .Development of MAC and PHY layers adds up to high data rates achieved by Wireless gigabit communication.