Sunday, 27 November 2016

Antennas for Small Cells and C-RAN

While a special antenna is not required for Small Cell deployment in general, they do require the right kind of antennas to make sure the original purpose of deployment is achieved.

Specifications for base-station antennas for use with small cells developed by NTT DOCOMO are shown in the picture above. The following is from the NTT Docomo Technical Journal:

These antennas feature dual polarization and can be shared among the 1.5 GHz and 1.7 GHz frequency bands. A separately developed compact duplexer is installed between the SRE and antenna to separate and combine signals of these frequency bands. The compact configuration of these antennas simplifies their installation.

When planning a service area by placing small cells next to each other, deterioration in signal quality due to interference between small cells is an issue of concern. To resolve this issue, downward tilting in the vertical plane is effective to reduce the interference caused by that antenna’s signals on adjacent cells while also to raise the receive level within the antenna’s own cell. The end result is improved throughput. The following summarizes the features of three types of antennas developed by NTT DOCOMO taking interference reduction and diverse installation environments into account.

1) Rod Antenna (Two Types): Having an omnidirectional radiation pattern in the horizontal plane, this type of antenna is installed on the wall or ceiling of a building to form a service area in its periphery. Two types of rod antennas have been developed: one with tilting for an interference-reduction effect and the other with no tilting for a compact configuration. The rod antenna with tilting consists of multiple vertically aligned antenna elements, the amplitude and phase of each of which is adjusted to produce an electrical tilt. The tilt angle, however, is predetermined.

2) Plane Antenna: This type of antenna has high gain while having a unidirectional radiation pattern making it applicable to installation on high places like building roofs to form a service area in a spot-like manner. A plane antenna can be given a mechanical tilt with a metal fixture to reduce interference.

Interested readers can download the article from here.

I also posted an article on the 3G4G blog titled 'Antenna evolution: From 4G to 5G'. The presentation by Kathrein provides more details on Small Cells and mmWave antennas. Why mmWave? Because most of the industry thinks that mmWave 5G will be small cells.

The relevant part is embedded below

As always, comments, insights and suggestions welcome.

Wednesday, 16 November 2016

Small Cells for Public Safety Communications

One of the many use cases for Small cells is for public safety communications. In case of emergency situations (earthquake, floods, terrorism, etc.) when the macro network is damaged or as it generally happens, the power supply is disrupted, small cells can quickly come in action and provide a coverage solution. This was discussed in an earlier post here.

Another scenario is when dedicated public safety coverage needs to be provided for hard to reach places or in a stadium kind if scenario, small cells be fill the void.

While in USA there is a dedicated band (Band 14 – 700MHz) available for use with public safety communications, most other countries do not rely on dedicated spectrum. In case there is no dedicated spectrum, there are still many different approaches to make sure that the personnel from emergency services can continue communication (as long as there is coverage available).

Parallel Wireless*, a Small Cells solution provider based in Nashua, NH, USA specializes in public safety and rural coverage solutions using small cells. The following slide pack contains some of their stories of deployments, demos and trials:

Further Reading:

*Full Disclosure: I work for Parallel Wireless as a Solutions Architect. This blog is maintained in my personal capacity and expresses my own views, not the views of my employer or anyone else. Anyone who knows me well would know this.

Thursday, 10 November 2016

Multi-vendor LTE Small Cells SON

Before we proceed further, in case the reader is not aware of Self-Organizing Networks (SON), please refer to my old tutorial here.

BT has recently published a white paper on multi-vendor LTE SON based on tests using LTE small cells provided by Node-H and Qucell. From the news posted on Node-H website:

The white paper focuses on the important issue of interference management between small cells. The paper is the result of a joint effort by British Telecom's Research and Innovation group and the technical teams of Qucell and Node-H. It addresses some of the major challenges of LTE HetNets and expands on the work of the 2016 ETSI Plugfest, which was run under the auspices of the Small Cell Forum. The authors’ conclusion is that interoperability between different vendors' SON implementations is achievable and so operators can look forward to robust, seamless and tailored solutions from multiple vendors.
The white paper shows that it is possible to operate mobile networks in which the individual LTE cells execute different ICIC algorithms. These findings challenge preconceptions about SON that are common in the mobile industry and make the case towards larger multi-vendor deployments of LTE small cells and call for bolder efforts in multi-vendor SON testing.
The ICIC algorithms used during these tests have been developed independently and without exchange of technical details between two separate HeNB vendors. Despite this, it has been shown that both algorithms can gracefully co-exist in the same LTE network. ICIC standardization efforts within 3GPP, along with the Small Cell Forum's Plugfest activities, have been key to this success.

The whitepaper embedded as follows and is available to download from here:

Related posts:

Saturday, 5 November 2016

Small Cell Installation Challenges

Today I decided to focus on an area which I don't normally look at much detail. While going out and about in the field, I can always notice the different types of deployments. Some are nice and clean while others are really messy like the ones in picture above.

While all of the situations cant be fixed easily, some of them require clever connectors that can simplify the connections. This presentation from Huber+Suhner embedded below provides some good solutions and examples.

Thursday, 20 October 2016

Carrier Aggregation (CA) and Dual Carrier (DC) enhancements in Release-13

Recently I posted a summary whitepaper of 3GPP Release-13 by 5G Americas. This article from NTT Docomo technical journal complements that nicely and provides in depth analysis of selected features.

The article (embedded below) focuses on Carrier Aggregation (CA),Dual Carrier (DC) enhancements, LAA and LWA. In this post, I am going to restrict the discussion to CA and DC.

The following is from the magazine article:

Carrier Aggregation (CA):

Up to Release 12 CA, a maximum of 5 LTE carriers called “Component Carriers” (CCs) could be configured for a User Equipment (UE). This enables a maximum 100 MHz bandwidth for data communications, which achieves a theoretical peak data rates of approximately 4 Gbps, assuming eight Multiple Input Multiple Output (MIMO) layers and 256 Quadrature Amplitude Modulation (QAM) for downlink, and 1.5 Gbps assuming four MIMO layers and 64QAM for uplink.

In Release 13, the maximum number number of CCs that can be configured for a UE simultaneously was increased to 32 to archive higher data transmission rates with wider bandwidths. This enables a maximum 640-MHz bandwidth for data transmission, achieving peak data rates of approximately 25 Gbps for downlink with 8 MIMO layers and 256QAM, and 9.6 Gbps for uplink with 4 MIMO layers and 64QAM.
Release 13 introduced the new function to enable PUCCH configuration for a Secondary Cell (SCell) in addition to the PCell in uplink CA. When CA is performed with this function, CCs are grouped together either with the PCell or SCell with PUCCH (PUCCH-SCell). UE sends UCI for CCs within each group by using the PCell or PUCCHSCell. With this new function, uplink radio resource shortages can be resolved by offloading UCI from macro cell to the small cells while keeping the macro cell as the PCell.

Dual Carrier (DC):

Release 12 designed DC to achieve user throughput comparable with that of CA by aggregating multiple CCs across two eNBs. In release 13, DC was further enhanced with higher uplink throughput and more flexible deployment.

In DC, separate eNBs allocate uplink resources independently for a UE. Hence, Release 13 addresses how to allocate adequate uplink resources on multiple CCs for UE. Typically, eNB calculates the required uplink resources based on the uplink buffer amount reported from UE. In DC, since both eNBs calculate the amount of uplink resources based on the report and allocate them to the UE independently, excess uplink resource allocation over actual amount of remaining data will occur. In particular, with small data packets, if resources are allocated by both eNBs, the UE may send all data to only one of them, and send padding (meaningless bit strings) to the other eNB, which wastes radio resources.

To prevent the excess uplink resource allocation for the small data packets described above, new uplink transmission control methods were introduced. In Release 13 DC, UE buffer status reporting and uplink data transmission are controlled based on the amount of uplink data buffered in the UE.

If the amount of the buffered data is smaller than the threshold configured by the eNB, the UE performs buffer status reporting and uplink data transmission only to one of the eNBs, just like DC in Release 12. In contrast, if the amount of the buffered data is larger than the threshold, the UE transmits to both eNBs. This buffer size-based mechanism solves the uplink resource over-allocation problem since only one eNB is aware of the buffered data and allocates resources when the amount of the buffered data is small.

The paper is embedded as follows:

Related posts:

Saturday, 8 October 2016

Thursday, 22 September 2016

Small Cell Forum workshop on 5G

I was having a twitter discussion earlier today as to whether 2G/3G should be switched off to make room for the more efficient 4G/4G+. While I agree with regards to the efficiency of 4G/4G+, there is still plenty of room for existing technologies, including 2G for a long time. 

While 5G is great and as can be seen in the picture above, a very optimistic picture has been painted with regards to LTE/5G.

Small cell forum recently held a workshop on 5G in Rome. Though it doesn't say explicitly, I am assuming the focus was Small Cells and 5G. It wouldn't be surprising as most of mmWave deployments would be comparatively small as compared to macrocells today.

I like this picture below as it shows that there are practical problems to solve today then worry about the 5G deployments of 2020. Having said that, the mobile community has to start preparing for it now to be ready by early 2020's  

Huawei had another interesting concept of how 5G HetNets will look

Nokia suggested that the lessons learned from Small Cells will help vendors with 5G deployments.

You can see all the presentations available here.

If you found something very interesting, please share in comments.

Monday, 5 September 2016

LTE Relay as a disruptive backhaul technology for Small Cells?

Came across this interesting presentation from Airspan which their CTO Paul Senior delivered at Small Cells World Summit in May. Here they are suggesting that relays could be used used on the cell edge to backhaul small cells and hence improve throughput for a UE that is camped on small cell. Probably much easier to understand from the picture below.

This approach is similar to in-band backhaul that is used by other vendors. I gave an example of in-band backhaul from Parallel Wireless in my Rural coverage post here. The advantage of relays & in-band backhaul is that the small cells could be deployed easily and also moved/relocated later on as there is no limitation due to backhaul provision.

In an article from last year on ThinkSmallCell, Paul said:

The 3GPP standard includes a feature to support remote relays at the cell edge, which only needs power to rebroadcast the signal into poor coverage areas. However, this requires a separate protocol stack in the macrocell – something which not all vendors have implemented.

Instead, we've built a simple relay using a directional antenna to the macro which operates at a different frequency band, say 2.6GHz TD-LTE, and rebroadcasts at 1800MHz FDD-LTE. The antenna form factor and design enables much better utilisation of the link that when serving smartphones directly, using 64QAM rather than QPSK to achieve much higher throughput within the same spectrum and macrocell resources. The short range radio link to the end users also provides the potential for higher speeds and better service quality. It's a quick and effective solution for enterprise buildings at the edge of coverage.

The potential capacity of an LTE Relay isn't insignificant. If we used LTE with 256QAM, 8x8 MIMO we could see a consistent throughputs of 450Mbps.

I could also see this being useful in transport applications, such as for Connected Cars. We'll be releasing products later this year for vehicle based solutions at various frequency bands.

They did demo some of the products in SCWS2016, which can be seen in another ThinkSmallCell report here.

The Airspan presentation is as follows:

Related posts:

Thursday, 25 August 2016

Small Cells vs Macro Cells Densification

Here is a presentation by KPN from Small Cells World Summit 2016 explaining how densification using small cells makes more sense than using macro cells. They have presented case study of Rembrandtplein to explain this. Feel free to add your views as comments.

Related posts: