|
5G/NR |
||
|
NOTE : Most of the contents of this page would not be so helpful or relavent anymore as of now (Dec 2020), but I would keep this because you may get some idea on what kind of discussions and/or activities are going on before we realize a new technology. NOTE : Since about a year ago (2019), there has been discussions about 6G. It would be good to track the 6G evolution path and check on how the path differs or same as 5G evolution path. I am keeping the initial 6G activities in this page.
Following is the topics I will talk about in this page.
Please don't waste your time if you are in any of the followings. i) I have already a lot of things in my plate and I am not interested in anything that would not become my job within next 5 years. ii) I am not interested in any technical issues that is not clearly defined
It would be worth spending sometime to read through this page and more importantly putting your own thought on this. i) I want to get ready for the technology that would come in several years ii) I wouldn't blame anybody and would not regret if the technology will not be realized. iii) I have a belief that there is no technical discussions which is totally useless, even when they are possibly wrong information.
In short, it is because I am a person who falls into the category described 'who should read this' section. Another reason is based on my experience (frustration) while I have been learning in this area (it is mainly for wireless communication, but i think it is similar to any other technology as well).
The first thing I tried was 'printing out whole 3GPP specification and trying to understand everything about the technology'. However, I started realizing that those documents keep adding new updates much faster than I read them (not to mention of understanding them) and it is almost impossible to catch up everything once those organization body start their jobs. There are hundreds/thousands of persons adding new pieces on those specification and I am only single person who is trying to understand all of them. Then I start to realize that one of the best way would be to start at very early stage of the technology, not even when it is formalized and when people start talking about something but nobody has any clear idea on it. Of course, it would be very confusing and in many cases those talks would not be very accurate... but still just following those initial talks (even technically not correct information) let you gradually form a overall concept on your own. If you go through this stage, you would be able to catch up all of those specification (actually those specification permeate into you like osmosis) when the technology gets formalized by a standard organization.
When I first got into this wireless communication (mobile communication) area, there has already been 5~6 years accumulation of 3GPP specification of UMTS and you may guess all the frustration that I went through. In LTE case, at least I could start reading from very early versions of 3GPP specification when the total volum is not that huge. But even for LTE, I wish I started reading on the fundamental technical background and catching up all the 3GPP TR(Technical Report) before the formal specification start being written.
And I thought... whatever the next technology will be, I will start before they are born. I will start tracking from the stage of fertilized egg. If I start looking at it when it is a new born baby, the baby will grow much faster than my brain can catch up. That's why I am start posting this. But I think this will be a single page post for several years putting a list of articles collected here and there, and purely my personal thought which may or may not be technically very accurate.
I don't know -:). Nothing about 5G is defined officially in any standard organization as of now. I would put the definition and features of 5G as more information/clarification comes out.
< Initial Definition >
When the first talk about 5G started and some of prototyping test result came out, the focus was mainly around throughput. (This kind of focus hasn't been changed much until mid 2013)
At least, one thing for sure will be that the data rate will be at least several G bps. (The final goal of 4G data rate is 1 Ghz and we still have a long way to go to achieve this 1Gb rate).
< Definition by METIS>
More organized and formal definition can be made from METIS which were proposed in Aug, 2013. Even though METIS does not put forth explicit 'definition', it proposes several KPI (Key Performance Indicator). I think we can say "A communication system satisfying the METIS KPI can be categorized as 5G". Following is the list of KIPs and test cases performing the measurement of KPIs proposed by METIS. (Refer to D1.1 and D2.1 METIS document for details)
Technical Requirement proposed by METIS to meet 5G goal are :
< Definition by 5GNOW >
5GNOW does not decribe much about high level definition or use model of 5G. I guess any 5G high level definition fall into the scope of METIS definition/use model. 5GNOW discuss more on lower level impelmentation of 5G. Key implementation Item discussed/proposed by 5GNOW is as follows.
After I've read most of 5GNOW Deliverable document, the key words that pop-up consitantly in my mind are
Think on your own why these would be issues and then refer to 5GNOW Deliverable Documents.
How will you achieve the technology ? what would be the challege ?
Since no technical specification is done for 5G, I cannot talk anything about any technology for 5G that is officially described. What I want to say in this section is just to think of some possible technical factors and challenges for those technical factors. Most of the comments for each factors would sound too pessimistic, but it has always been like this before any new technology come out, but I believe eventually most of these challenges will be overcome or totally new concept that can overcome these obstacles will emerge. This is how all the current technologies have evolved. The purpose of my comments here to give you something to think about.
One thing for sure for 5G would be that the required data throughput for 5G will be much higher (probably tens of Gbps) than 4G. So I want to talk about general technique for increasing the data rate.
< Increasing Modulation Depth >
Whenever a technology reach a point where it has to jump up the data rate, one of the first step has almost always been "to increase Modulate Depth". The most common evolution path for the modulation Scheme was as follows : BPSK -> QPSK(QAM) -> 16 QAM -> 64 QAM What would be the next step ? Logically it should be 256 QAM. (If it is too much, we may think about 128 QAM) Would this be possible ? It may be possible if it is wired, it may be possible (possible but not easy even in wired communication). However, it would be very difficult (almost impossible ?) with wireless communication when we think about various wireless factors (AWGN, Fading, Avaliable Power, Dynamic Range, PAPR handling etc).
< Increasing Number of Antenna and Spatial Multiplexing factors >
When we reach the maximum modulation depth, another step we think of as the next step to push up the throughput would be to increase the number of antenna and Spatial Multiplexing factors. The most common Antenna Configuration for multiplexing we use the most commonly as of now (as of May,2013) is 2 x 2 MIMO. The maximum configuration that is specified in 3GPP as part of final goal of LTE advanced is 8 x 8. Considering the 5G data rate will be much higher than the final stage data rate for LTE advanced, it is highly probable to adopt even more entenna (more complicating Spatial Multiplexing). How many antenna we can use ? How difficult it would be ? We don't know... but the number of Antenna that SamSung claimed to use for their next generation technology trial (May 2013) was 64 antenna array. Would this be really feasible/practical ? Look at the mobile phone that you have now and imagine that you have to put a 64 antenna properly spaced for maximize the spatial multiplexing. At least, Antenna and RF designer would not want to even think about it -:)
< Increasing the operating bandwidth >
If all the other technique mentioned above is not possible, an alternative we can think of is to increase the channel bandwidth (RF bandwidth). What is the maximum bandwidth we use for LTE as of now ? (May 2013) It is 20 Mhz assuming Single Carrier. If we adopt LTE advanced technically available as of now, it can be max 40 Mhz using Carrier Aggregation with 2 carriers. At the final stage of LTE advanced, we may be able to use max 100 Mhz using 5 carriers. If you think about 100 Mhz for the currently available spectrum (mostly 800~3Ghz), first you would have spectrum license issue. Most of the spectrum is already sold out. Another issue would be to develop various RF components to handle 100 Mhz contiguous spectrum. 100 Mhz single band would be too much fractional bandwidth (operational bandwidth divided by the center frequency). You can think of implementing 100 Mhz using 5 separate 20 Mhz band, but in that case you need to implement 5 separate RF chains for it which will make RF/hardware design so complicated.
< Using very high frequency spectrum >
One of the ways to get around the 'increasing operating bandwidth' issues described above would be to use very high frequency spectrum which has not been licensed out much. For example, if you go to 20 Ghz spectrum, 100 Mhz BW is only 0.5 % fractional bandwidth.. and several hundreds of Mhz BW is less than 5%. In case of recent SamSung trial (May 2013), it is claimed to use 26 Ghz spectrum. But one of the biggest problem with this kind of high frequency (millimeter wave) is that it has extremly high path loss and is very vulnerable to various envirenmental/weather factors like building, tree, moisture, rain etc. Another important problem with this kind of high frequency is that it would be very difficult to get the small sized RF components properly working at this frequency. (For example, RF SAW duplexer, SAW filters which are one of the most commonly used components in the mobile phone currently will not be used in these frequency.)
One area that can be more practical at least as of now (July 2013) would be in 5Ghz range since the chipsets and devices supporting 802.11ac are already emerging in the market even though the performance may not exactly meet the claimed criteria. However, it would be pretty sure that higher and wider spectrum will be considered as well in real 5G mobile communication.
< Dynamically Configurable Spectrum both in frequency and time domain >
Unlike the current communication system, it is expected that multiple radio technology, operators and carrier frequencies would change dymanically even during the signal user service session. If you think of LTE-A Carrier Aggregation, WiFi Offload, it would give you very primitive idea of this. But this kind of combination and dynamic changes will become a default mode of operation in 5G. Then.. the challenging issue would be how the RF front end of the device handle this kind of situation.
If I am asked to list a couple of critical features that should be accomplished in 5G before anything else, I would list as follows :
Even though it is not a single solution that can completely achieve all these features, one of the key factor would be Massive MIMO (In case of the prototype that SamSung came up with in May 2013, it used 64 Antenna in 28 Ghz). I stronly recommend you google this topic and study. Following is a couple of introductary material that I found.
< Very Short TTI and Extremly Low Latency >
These property can be described in several different layers..but usually when we talk about TTI it usually refer to MAC/PHY property and when we talk about Latency it usually refer to higher layer including IP layer. Regarding TTI, in WCDMA R99 the most common MAC layer TTI were 10 ms (U-Plane) or 40 ms (C-Plane), in HSPA it become 2ms or 10 ms, in LTE it become 1 ms. I think 1 ms is already a kind of min TTI, but we would need event shorter TTI to achieve the max throughput/latency criteria required for 5G. Another possibility would be that a couple of additional TTI is introduced and let the system select one of the TTI dynamically or semi-statically depending on situations.
< Extremely High Sampling Rate ADC/DAC >
Even thought nothing specific is formally defined for 5G requirement, I think it will be highly probable that the system bandwith will get extended to at least a couple of hundreds Mhz. As I mentioned above, there will be a lot of issues related to RF (or milimeter wave) but there will also be tough chalenges at baseband level as well. The first question you would have would be "what would be the sampling rate ?". If the system bandwidth at carrier frequency level is a couple of Mhz, the sampling rate at baseband level should be several Mhz BW. It means that you need ADC which can sample and convert at several Mhz rate. You may think this would not be a big issue since you may have seen various digital oscilloscope which covers even a couple of Gb sampling rate. Yes.. it is true. This kind of super high frequency ADC is already used in various area especially high end digital oscilloscope. But those high frequency sampling is not done by a single ADC. It is done by multiple ADCs working in parallel and sampling in interleaving pattern. To make this kind of sampling work properly, very complicated hardware design and control algorithm are required. To make this kind of technology usable for a mobile device which should not be as expensive and bulky as a high end digital oscilloscope, great deal of improvement on ADC/DAC technology is required as well.
See if following materials can give you any insight on this topic. (Think of how you can make this kind of technology usuable on mobile device)
< RACH mechanism to handle very large numbers of subscribers >
One of the important goal of 5G is to implement a system that can handle very large numbers of subscribers. These subscribers are not only human but also various types of machines and sensors. In this case, the chances would increase a lot of PRACH reaching a network simultaneously and casuing contention. To figure out a way to handle this situation will be an important topics to be researched (especially in MAC layer design).
This section mostly give you lists of ariticles or YouTube demonstration that is targeted for '5G' technology. Almost nothing in these articles would explicitly use the word '5G'. Some say "Next Generation" and some say "Beyond LTE" and some say in other way. But I think all of these will be key components of whatever comes after 4G.
Now a new Orgnanization has been initiated to lead specification of 5G. I would be interesting to see how the dynamics would go between 3GPP and 5G PPP about 5G Initiative.
Finally 3GPP start presenting things about 5G.
< METIS (Mobile and wireless communications Enablers for the Twenty-twenty Information Society) >
Now it seems that this consortium is becoming the leading driver for 5G at least in terms of technically defininng what 5G should be like. My guess would be that a lot of ideas from this consortium would be reflected on future 3GPP for 5G. I strongly recommend you follow up these documents.
You can get a lot of details information from here especially possible PHY/MAC implementation including various way of Waveform creation. Go [Download] and download Deliverable Documents.
< SamSung : Next Generation Wireless >
Recently (May 2013), SamSung claims that they have implemented a technology to achieve the data rate of 'tens of Gbps'. Some articles is about SamSung's claim and some other articles are from critics which dispute SamSung's claim. I don't think whether this claim is practically achievable or whether the claims are technically accurate is important. Both the claim and dispute about the claim would give you some insight on next generation technology.
You can find many presentations and whitepapers with practical test/simulation data especially with Focus on milimeter wave Radio Access Network.
No technical information is mentioned in this article, but based on what they have done until 4G, it would be worth following up what Erricsson plans. You will see an interesting contrasts from the first two aricles coming out in around 2 years interval. I am not trying to criticise on anything... this is a kind of normal opinion/mentality changes for almost all revolutionary technology.
They claims that they achieved 10 Gbps throughput in 11 Ghz, 400 Mhz BW with 24 antenna.
Huawei released a couple of articles about their plan for future technology sometime around Mar, 2012. Almost no detailed technical information is mentioned in these articles, but you can at least have some 'feeling' about what they intend to do.
Even though the WiFi (mainly based on IEEE specification) would not be exactly same as Mobile communication technology (mainly based on 3GPP specifiction), nobody would deny the fact that these two big bodies has been influencing each other for a long time. (Think about.. OFDM based WiFi --> WiMax --> LTE). Recently (as of July 2013), a lot of discussions are going on about 802.11ac which claim to support over 1Gb data rate and we already see some chipsets and real implementations are coming out.
Actually I would not call this as 5G. Technically I should call this as 'final target of 4G' which is targeted for 1 Gbps data rate. But I put this on this page because it shows a real demo (even though it is physical layer only and in very short distance) and I think this will be an important building block of next generation communication as well.
At least as of now (May 2013), it seems these material are most technical on the future technology.
You would get the most concrete idea on 3G at least as of now (June 2013).
This company released a test bed for Massive MIMO
This is a huge list of the articles. so I kept these articles in a separate page : here.
I keep this in a separage page : here.
|
||
