xR beyond Pokémon Go

Singapore’s Changi airport is one of the world’s best airports, not only from the services, facilities and infrastructure, but also in terms customer/client engagement. Changi is very much in synchronization with what happens elsewhere in the world. The appearance of the lounges changes very frequently to adopt to a current theme, be it Star Wars or any other latest film release. Pokémon Go, the latest location based Augment Reality (AR) game developed by Niantic, was no exception. Airport wide advertising could be seen inviting passengers to capture Pokémons. Sounds weird, but this is where the world is moving today. Different forms of Digital Senses are being introduced, including AR, Virtual Reality (VR) and Human Augmentation (HA), blurring the lines between the virtual and real worlds.

I’ve used xR to mean “anything Reality” as we now have different forms of realities - AR, VR, HA and possibly many to come in the future. All these things are related to how humans see/visualize things from their eyes and feel based on that. If you are not blind, you naked eyes allow you to see everything around you in three dimensions (3D). That’s real reality. By using different accessories, like smart phones, smart glasses and smart gears, we can see different forms of realities and the most widely used ones today are AR and VR.  

• AR brings computer-generated graphics to life, superimposing near lifelike, digitally processed images on what the person actually sees in the real world (ex:- Pokémon)
• VR immerses people inside virtual worlds that mimic the real one or fictitious ones.
• HA (sometimes referred to as “Human 2.0”) focuses on creating cognitive and physical improvements as an integral part of the human body, sometimes combined with VR applications.

While there are pros and cons of xR, we can certainly take it beyond Pokémon Go, solving some of the real world problems. Let’s look at some of them in little detail.

 

Hands-free reference

If you are repairing or operating a complex machinery or equipment, you need to refer to its user manual. User manuals are either in printed or digital formats and need to be read on paper or on digital display like a tablet or laptop. Both need the use of your hands. If we can have an AR helmet with the wiser as an AR display or a pair of goggles with the glass as a display, we can free up our both hands to do the work more easily and effectively. The display will display the instruction manuals or videos for easy reference. In built cameras, motion sensors and gesture sensors can manually or automatically control the information to be displayed.  

 

Virtual therapy

Anxiety, depression and different forms of stresses can be addressed if the patient or the person in question can be exposed to VR worlds of different attributes, instead to a real world. For example, if someone has a fear of speaking to large crowds, we can simulate a large crowd on a VR headset and ask the person to practice the speech/ talk at his own convenience. The crowd could be dynamic with motions and sounds.

 

Disaster Recovery training

How to behave in a disaster is something very difficult to train, unless you’ve faced a one on your own. But, today we can use VR to immerse you in a disaster situation and train you in a real lifelike environment as to what to do and how to do to save your own life and the lives of others.

 

Criminal trials

One of the difficulties in doing a criminal trials is the difficulty in visualizing the real crime scene. The legal system usually relies on material evidences, photos and drawings. If the jury can be given a facility to virtually be in the crime scene using VR, it will surely enhance the knowledge about the surrounding, fine details etc. and will surely help the correct and efficient decision making. The present legal system will surely take some time to use this type of technologies for the legal process, but this is certainly an option.

 

Witnessing news, instead of watching

Traditional news is delivered either to listen or watch. The real feeling, for example, the news reporter has on the ground (ex:- battle field) is not really transferred to the viewer. If we can have VR based news, the viewer can actually immerse in the situation and actually feel the news. This can be used for live events also.


I’ve listed only few possibilities of  xR and you can see the possibilities are actually endless. As xR is getting closer to reality, will people eventually prefer the virtual over the real world? I don’t know yet. Let’s wait and see what xR can really do to the human mind and eventually to the society at large.

Have we taken computing, bit storage and bit transport for granted?

If you over heard the terms IoT (internet of Things), AI (Artificial intelligence),  VR (Virtual Reality), AR (Augmented Reality), AV (Autonomous Vehicles) and many others alike, during the past couple of years, especially in the beautiful city of Barcelona - if you happened to be at MWC (Mobile World Congress) 2017, then you’re not the only one. Celicitaciones! (On a different note, I also thought to myself that the abbreviations are also becoming shorter – 2 letters instead of 3 /4 letters).

All of a sudden, the terms we used to hear and discuss often – like IP (Internet Protocol), Ethernet, MPLS (Multi-Protocol Label Switching) - in the Telecom industry have been replaced by a set of more sexy terms like IoT, AI, VR, AR, AV, etc. These new techs have also broken the boundaries of traditional Telco industry and many cross disciplines – like medical, education, transportation, trading, finance, etc.- have been interconnected like never before.
But, one thing that most of the new technologies seems to be taken for granted is the presence of readily available underlying infrastructure, mainly consist of computing, bit storage and bit transport. These are the three fundamental tasks we have been doing in the entire history of ICT (Information and Communications Technology). No doubt that these three areas have also been improved and matured over the years and today we have super computers capable of super-fast computing,  DCs (Data Centers) with massive capacities and networks with Terabit bandwidths.

However, as IoT, AI, VR, AR, AV, etc, are commoditizing and commercializing in a rapid pace than we thought, can we simply take the infrastructure for granted? The size and shape of different vectors like scale, capacity, responsiveness, etc. on the infrastructure to support the requirements of overlay services/applications might suddenly create catastrophes, if we do not prepare ourselves today. It’s a good sign that we now see, at least in small scale, some discussions happen across these areas. Don’t be surprised the next time you go to an optical conference, and you hear someone talking about VR/AR.

What is required is a more collaborated discussions and researches to view and address the total requirement as a whole, making sure to include all the stakeholders. These stakeholders surely will not come entirely from telecom domain, but from different other domains we might never have thought of.

In search of a Multiple Access Scheme (MAS) for 5G

5G – the 5^th Generation mobile technology might arrive at our door steps sooner than we think, supporting 3 typical usage scenarios: enhanced Mobile Broadband (eMBB), massive Machine Type Communication (mMTC) and Ultra-reliable Low Latency Communication (URLLC) [1]. Though architecture wise 5G is different from its predecessors, like in any other wireless communication technology, among many other things, the Multiple Access Scheme (MAS) becomes the key for 5G and selecting the suitable scheme will ultimately decide the future and success of 5G.

MAS (aka Multiple Access Method or Channel Access Method) is required when we have to share a physical media. This is not only applicable to wireless, but also to many wired networks including bus networks and ring networks. In wireless, MAS allows several User Equipment (UE) connected to the same multi-point transmission medium to transmit over it and to share the available radio capacity. MAS is based on a multiplexing method, allowing several data streams or signals to share the same communication channel or physical medium.

Multiplexing or muxing works by combining multiple analog or digital signals into one signal over a shared medium. Space Division Multiplexing (SDM), Frequency Division Multiplexing (FDM), Time Division Multiplexing (TDM) and Code Division Multiplexing (CDM) are some examples. Therefore the MAS using FDM becomes Frequency Division Multiple Access (FDMA), TDM becomes Time Division Multiple Access (TDMA) and CDM becomes Code Division Multiple Access (CDMA).  In FDMA, each user has a small part of the resource (spectrum) allocated all the time. In TDMA, each user has nearly all the spectrum allocated at a small duration of time. In CDMA, each user has all the spectrum all the time. While multiplexing is provided by the physical layer, multiple accesses also involves Media Access Control (MAC) layer.

So, in summary, Multiplexing is combining many signals on one media, while MAS is allowing many to access the media/resource at one time. Therefore, it can be stated that Multiplexing is a technique and multiple accesses is the way to use that technique.

Over the years, different generations of mobile technologies used different MASs to achieve different capabilities, more importantly the system capacity and spectral efficiency. 

Generation	MAS	Application
1G	FDMA	AMPS
2G	TDMA	GSM
3G	CDMA	UMTS
4G	OFDMA	LTE

Note: AMPS-Advanced Mobile Phone System, GSM-Global System for Mobile communications, UMTS-Universal Mobile Telecommunications System, LTE-Long Term Evolution

All the above MASs (except CDMA), which can be called as conventional MASs, are Orthogonal Multiple Access (OMA) technologies.  In OMA, different users are allocated to orthogonal resources in either time, frequency or code domain in order to mitigate Multiple Access Interference (MAI). As the expectations or the objectives of 5G (higher data rates – 100/1000 times 4G, low latency – 1ms Round Trip Time (RTT), massive connectivity, high density – 1M devices/km^2, enhanced indoor coverage etc.) are quite different from that of 4G and others, the Radio Access Technology (RAT), which is characterized by MAS, need to be flexible, reliable, energy efficient, spectral efficient and support diverse Quality of Service (QoS). OMA schemes are not sufficient to support these requirements, especially massive connectivity and diverse QoS. [2], [3], [4]

It’s worthwhile to look little deeper on the scenario of mMTC and why the current LTE or LTE- Advanced (LTE-A) will find it difficult to support mMTC. In LTE/LTE-A there are lot of interactive processes between the Node B (NB)/enhanced NB (eNB) and the UE before data is transmitted. This is ok for long time continuous sessions, as the signaling overhead averaged over time is less. However, in mMTC used in Internet of Things (IoT), the “thing” (including UE) transmits a small amount of data over s short period of time and there are millions of such “things”. Now if we use LTE/LTE-A for such a scenario, the signaling overhead suddenly becomes high and access efficiency becomes low.

Therefore, several Non-Orthogonal Multiple Access Schemes are proposed for 5G, especially to address the Machine-to-Machine (M2M) requirements. These include; Superposition Coding based Non-Orthogonal Multiple Access (SPC-NOMA), Multi –User Shared Access (MUSA), Sparse Code Multiple Access (SCMA), Pattern Division Multiple Access (PDMA), Resource Spread Multiple Access (RSMA), Non-orthogonal Coded Multiple Access (NCMA) and Interleaver-Grid Multiple Access (IGMA). The different Non-Orthogonal Multiple Access Schemes can be compared as below; [1], [5]

Category	Power Domain Based	Code Domain Based					Interleaver Based
	SPC-NOMA	MUSA	SCMA	PDMA	RSMA	NCMA	IGMA
Scenario	DL: eMBB	UL: mMTC, URLLC DL: eMBB	UL: mMTC, URLLC DL: eMBB	UL: mMTC, URLLC DL: eMBB	UL: mMTC, URLLC	UL: eMBB mMTC, URLLC	UL: eMBB , mMTC, URLLC
Multiplexing Domain	Power	Code/ Power	Code/ Power	Code/ Power/ Spectral	Code/ Power	Code	Interleaver
Transmitting Overhead	Low/ Medium	High	Medium/ High	Medium/ High	Low	High	High

Note: UL-Uplink, DL-Downlink

When we design Non-Orthogonal Multiple Access Schemes, we need to consider following;

• Coverage
• Peak to Average Power Ratio (PAPR)
• Implementation Complexity
• Combination with Multiple –Input Multiple-Output (MIMO)
• Flexibility

Pictorially, TDMA, FDMA, CDMA, OFDMA and NOMA can be visualized as follows [6]. This shows how different users (denoted by different colors) gets the allocation of spectrum.

While there are multiple candidates for the 5G MAS in non-orthogonal domain, none of them seems to be a perfect choice at this point of time. As different schemes have both their merits and demerits, it’s likely that a combination of different MASs, including the conventional orthogonal schemes, will be used in 5G to achieve different objectives. However, as we get closer to 2020, where the finalized standards are expected to be released, more improvements on different schemes are possible with the expectation of all new schemes or approaches to combine different schemes. At the meantime, Research & Development Engineers and scientists will be quite busy discovering, improving and innovating the finest ingredients for the success of 5G.

References

[1] SUN Qi, WANG Sen, HAN Shuangfeng et al., “Unified Framework Towards Flexible Multiple Access Scheme for 5G” ZTE Communications, vol. 14, no. 4, pp. 26-33, October. 2016. doi: 10.3969/j.issn.1673-5188.2016.04.004

[2] WEI Zhiqiang, YUAN Jinhong, Derrick Wing Kwan Ng, et al., “A Survey of Downlink Non-Orthogonal Multiple Access for 5G Wireless Communication Networks”  ZTE Communications, vol. 14, no. 4, pp. 17- 23, October. 2016. doi: 10.3969/j.issn.1673-5188.2016.04.003

[3] Volker Jungnickel, Konstantinos Manolakis, Wolfgang Zirwas et al., “The Role of Small Cells, Coordinated Multipoint, and Massive MIMO in 5G” IEEE Communications Magazine, pp. 44-51, May. 2014.

[4] Peng Wang, Jun Xiao, Li Ping, “Comparison of Orthogonal and Non-Orthogonal Approaches to Future Wireless Cellular Systems”.

[5] YAN Chunlin, YUAN Zhifeng, LI Weimin et al., “Non-Orthogonal Multiple Access Schemes for 5G”  ZTE Communications, vol. 14, no. 4, pp. 11-16, October. 2016. doi: 10.3969/j.issn.1673-5188.2016.04.002

[6] Mahyar Shirvanimoghaddam, Sarah J. Johnson, “Multiple Access Technologies for Cellular M2M Communications”  ZTE Communications, vol. 14, no. 4, pp. 11-16, October. 2016. doi: 10.3969/j.issn.1673-5188.2016.04.006