Millimeter Wave MIMO Systems for 5G Access Networks

Guest post by Faris Alfarhan*

Cellular NetworkConventionally, millimeter wave (mmW) frequency bands have been either largely overlooked or treated solely as real estate for wireless backhaul and personal indoor networks. That is mainly due to higher atmospheric attenuation loss, penetration losses, and increased absorption and scattering in rainy conditions. However, recent measurements indicate good outdoor short range coverage – of 200 meters on average – when using directive antenna beams, even when radio line of sight conditions are not met [1-3]. The propagation characteristics of mmW bands vary considerably depending on whether LOS or NLOS conditions are present. Since mmW signals experience low diffraction due to their small wavelength, LOS signals propagate in conditions similar to free space (a path loss exponent of 2 on average). NLOS signals, on the contrary, experience more significant losses and hence a pathloss exponent of 5.7 on average [3]. However, the NLOS pathloss exponent is significantly reduced when directing the Tx and Rx antenna beams towards each other. In order to overcome the increased pathloss at mmW frequencies, directional beamforming or beamsteering is used to generate narrow beams towards users. Since the required antenna size is inversely proportional to the operating frequency, mmW antenna arrays could encompass as much as 64-256 antenna elements at the base station and 4-12 elements on a mobile device. For example, the required antenna element length is about 0.5 cm at 28 GHz,whereas it is about 20 cm at 700 MHz. Figure 1 shows measurement results for the maximum coverage distance of a mmW systems operating at 28 GHz as a function of the pathloss exponent and the combined Tx-Rx antenna gains, where acceptable coverage is deemed to have an SNR of 10 dB and higher. Continue reading →

It’s All Too Good To Keep Talking About The Capacity Problem

TalkingThe capacity problem is at the heart of everything said about the wireless industry. Everybody loves to talk about this problem. To start, it is easy to give examples of exploding data consumption forecasts or quote numbers on mobile applications such as Facebook, Twitter , Instagram and many others. I suspect that the capacity problem makes for a convenient argument for the different players in the mobile value chain to get what they want: it is a nice problem for everyone to have. For service provider side, it is the key to more frequency spectrum which further enhances increases their position in the market and consequently their value.  For solution vendors it gives them the opportunity to raise money, fund development projects and present forecasts for high revenues. For regulators it gives them the opportunity to sell spectrum and raise money. So everyone can benefit from the capacity problem, or so it seems. Continue reading →

Should Licensed Spectrum be Allocated to IoT Applications?

IoT ConnectivityA mix of connectivity technologies combines to enable the Internet of Things. These technologies can be complementary or competitive in nature. Determining which fits and which does not starts with the application use case and the user requirement. For most IoT applications there is no need for broadband connectivity. Rather, what is required is a reliable connectivity to transmit intermittent data cost effectively. This includes low maintenance and serviceability and low power consumption. To address such applications, new standards are emerging for low power wide area (LPWA) connectivity with operations in unlicensed bands such as 900 MHz or TV whitespaces. But that leaves connectivity subject to external interference that cannot be managed. Hence, should there be a dedicated spectrum for IoT applications? Continue reading →

The IoT Value Chain: Where’s the Value?

IoT Internet of things$19 Trillion is a lot of money. That’s the value Cisco expect the Internet of Things (IoT) market will generate over the next 10 years. Compare with annual world GDP of 75 Trillion, IoT will make for about 2%. Not bad. In terms of devices, the talk is for 50 billion connected devices in 2020, other estimates from ABI put the number at 30 billion and JP Morgan feels more like 75 billion in 2020; no matter, there will be a lot of devices! With this context, no wonder companies are salivating at the opportunity IoT brings about for new revenues streams and profits. But where will the value be and how can it be captured? This question is surely on the mind and lips of executives and the subject of discussion in many boardrooms. Continue reading →

Defining the Innovation Band and Shared Spectrum Access

3.5 GHz Shared Spectrum RulesSpectrum sharing rules for the 3.5 GHz band in the US are beginning to take shape. While there are still some important aspects to define, the broad lines have been drawn for the Citizens Broadband Radio Service (CBRS). The process of fine-tuning the rules will continue following the April Further Notice of Proposed Rulemaking (FNPRM) (comments are due July 14th and reply comments by August 1st). The proposed rules will have a three-tiered spectrum sharing scheme in 3550 – 3650 MHz between Incumbent Access, Priority Access License (PAL) and General Authorized Access (GAA) users. Furthermore, there door is open to roll into this band the 3650 – 3700 MHz band which today operates on a non-exclusive licensed basis. Continue reading →

Raising the Stakes in 3.5 GHz: LTE-Advanced Achieves 1 Gbps

1Gbps LTE-AThe 3 GHz frequency bands stands at the upper limit of what is considered today as viable spectrum for mobile communications. But bands 42 (3400 – 3600 MHz) and 43 (3600 – 3800 MHz) are not only the ‘last frontier’, but more importantly, they provide the widest spectrum of any other band (200 MHz). Additionally, the relatively short wavelength is perfect to enable advanced antenna system technologies based on beamforming and massive MIMO techniques. Couple these with the limited range of propagation that limits interference and the 3.5 GHz band becomes an interesting proposition for capacity starved operators. Continue reading →

Small Cells Progress Report – Challenges and Opportunities.

Small cells I have just released a new research report on the progress of small cell deployments in collaboration with ExelixistNet:  “Small Cell Ecosystem: Challenges and Opportunities.” The report examines mobile operators’ plans and deployment strategies of small cells and backhaul solutions along with vendor and technology preferences. The research is based on experience gathered by operators from market trials of small cells and wireless backhaul solutions conducted to evaluate the ecosystem deployment readiness and impact of small cell roll-out on operator financials and network performance. Continue reading →

SON Progress Report: A Lot Still to Be Done!

SONSince the first building blocks of SON were laid down around 2008 by 3GPP and NGMN, uptake in SON deployments has been very selective by a few leading carriers for some use cases. However, universal applicability remains elusive. To say the least, the SON market is struggling – but why, and how that can be turned around is what interests me. Having just attended the SON USA conference, I had made a few observations and like to put some down here. Continue reading →

Further Enhanced ICIC (FeICIC)

FeICIC LTE-AdvancedGuest post by Faris Alfarhan*

In an earlier post, R10-LTE enhanced inter-cell interference coordination (eICIC) techniques for heterogeneous networks were discussed, along with the concept of small cell range expansion. The purpose of cell range expansion is to offload more traffic from macro cells to small cells and hence achieve larger cell splitting gains. By adding a cell selection bias, the service area of small cells increases and more users are offloaded to small cells. The need for heterogeneous networks interference management schemes stems from the fact that users in the small cell range expansion area are vulnerable to stronger interference signals than useful signals from the associated serving small cell. In the previous post, it was explained how time domain partitioning based eICIC schemes – known as Almost Blank Subframes (ABS) – could be used to control the interference on the data channels in the range expansion region. Further, carrier aggregation based techniques – known as Cross Carrier Scheduling – could be used to control interference on the control channels (such as the PDCCH, PCFICH, and PHICH channels). However, R10 eICIC schemes did not address interference control on cell-specific reference signals (CRS), which cannot be blanked in order to ensure backward compatibility with R8 and R9 UEs. In this post, R11 improvements to eICIC schemes are discussed, along with the shortcomings of R10 eICIC schemes. First, the concept of Reduced Power Almost Blank Subframes (RP-ABS) is explained along with its advantages over ABS. I then discuss the R11 techniques of Further enhanced ICIC (FeICIC) to control the interference on CRS resources. Continue reading →

Trends in Wireless Network Densification

Small Cells - Network DensificationOne of the main trends in radio access network (RAN) is the bifurcation of systems that enable network densification. Today, mobile network operators have more options than ever before for the means of providing service to their subscribers. Alongside the evolution of wireless standards to provide higher spectral efficiency, vendors have unleashed a wide variety of radio access nodes. While the macro cell remains the workhorse, small cells, distributed antenna systems (DAS), distributed radio systems (DRS) and Cloud RAN (CRAN) are systems that will see increasingly wider deployment in the future. Given this, what are some of the trends that we see in this space? Continue reading →

Free Space Optics: An Overview of Market and Technology

Free space opticsFree space optical (FSO) technology in commercial applications has been around for a couple of decades now. During this time, significant developments happened to improve the utility and reduce cost. Today’s systems pack more capacity in smaller volume and at lower price while measures to improve reliability are integrated into the solutions to increase the robustness of the link.  Yet, the commercial applications of FSO remain in niche segments without a major breakthrough into mainstream markets such as mobile backhaul. In this article, I like to review the basic elements of the FSO market to shed some light on this segment of backhaul that has lived in the shadow of RF technologies. Continue reading →

From LTE-U to LTE-DSA: Solving The Capacity Crunch

LTE-UThe proposal by Qualcomm to enable LTE operation in unlicensed band (LTE-U) received a warm response from some (e.g. Ericsson, Verizon) and not so warm from others especially incumbents with strong legacy in Wi-Fi in both the vendor and operator communities. The contentious issue center on co-existence of LTE and Wi-Fi in the same band as Wi-Fi implements ‘listen before talk’ or in technical terms carrier sense multiple access (CSMA) as opposed to LTE where transmissions are scheduled by the base station. This issue plagued WiMAX in unlicensed bands and was topic of much work at the IEEE during standardization activities of that technology. Still, while the proposal is not yet an approved work item for 3GPP LTE Release 13, the next few weeks will most likely see this feature approved to include in the standard with completion timelines by end of 1Q 2016, when we very possibly can see actual systems deployed. Continue reading →

Data Sciences and Big Data in Telecom: A Big Deal?

Data SciencesThere is much hype in telecom. In just about every aspect of the network, new trends are shaping up: from the core to the radio access and through the transport network; in hardware, in software and in processes, buzz words and acronyms are aplenty. Worse, how often these acronyms are used out of context just to latch on a popular wave in a vain hope of marketing advantage? No wonder one can feel confused, even discouraged at times. What is real and what’s not? Who can really tell when there’s so much noise that masks real progress! Continue reading →

Observations on MWC 2014 – My Takeaways

Saddlenode BifurcationIn a nutshell, the wireless industry keeps on getting broader and more bifurcated. This is the main trend that has been around for years and that will not stop. Communication is becoming truly pervasive. Opportunities and confusion are intermingled. To understand it all, one needs to cut across wider breadth and dive into greater depth to separate hype from reality. This is a challenge all in its own. Separating the real from the fake is harder than ever!

In this year’s edition, some of my observations are: Continue reading →

Is the Personal Cell Technology for Real?

SONThe media is abuzz with the news of the pCell wireless technology – after all, it’s not too often that someone comes out and claims to have a technology that will change the world! For now, too little has been revealed on this technology, which is understandable for a startup.  The aura of mystery is necessary to fuel the hype machine. So, what can we deduce from what little has been revealed? And, what are the prospects of such technology? I will outline here a few thoughts to start this conversation and I look forward to your observations and opinion. Continue reading →