The battle between HomePlug and HomeGrid to emerge as the de-facto powerline networking standard was quite interesting between 2010 and 2013. However, despite silicon getting demonstrated at various trade shows, HomeGrid's G.hn was unable to get a retail product out for a long time. This changed last summer with the introduction of the Comtrend PG-9172, a 1200 Mbps G.hn powerline adapter.

Background

We have covered powerline networking on-and-off over the last five years. Around the 2012 time-frame, there was a big tussle going on between HomePlug and HomeGrid to emerge as the standard for powerline communication. HomePlug has been enjoying a lot of success over the last decade as the incumbent with a huge install base (both amongst service providers and retail consumers). Sigma Designs impressed us with multiple silicon demonstrations back in 2011. This was followed by Marvell throwing its hat in the ring later that year. However, despite multiple launches following up, HomeGrid's G.hn never appeared to gain traction.

At CES 2014, I had the chance to talk with the people from both HomePlug and HomeGrid. Following that, I completely wrote off G.hn's chances in the retail powerline communication market. My reasons were pretty clear - three years after launch of the first generation silicon from multiple vendors, they had no retail product to show. There were no major updates at CES 2015 either, and I thought HomePlug had sealed the deal to be the de-facto powerline standard.

Throughout this time, G.hn appeared to be gaining traction amongst service providers, but there appeared to be no significant deployment. Things started changing in 2015. Last year, Comtrend introduced the first G.hn product in the retail channel in the US market. We have had the review units for close to a year now. Despite doing some initial benchmarking last year, we were hesitant to carry out a full-length review with just benchmarks from the PG-9172 alone. Another reason was that the Comtrend PG-9172 was a standalone product, and couldn't inter-operate with the large number of HomePlug products already in the market. It was hard to judge the value of a product that had to rely on support from a non-Tier-1 vendor. A few weeks back, ARRIS (famous for its SURFboard cable modems after the 2013 purchase of the Motorola Home division) introduced the RipCurrent range of networking products utilizing G.hn technology. Suddenly, we could look at the Comtrend PG-9172 in a whole new light. A growing G.hn retail ecosystem meant that it was time to dust off the powerline adapters and look at the comparative performance of the PG-9172 against various solutions from the HomePlug stable.

Comtrend PG-9172: Features and Usage Impressions

The Comtrend PG-9172 is a powerline adapter based on G.hn technology. Prior to its launch, all retail powerline adapters had been based on HomePlug technology. Readers looking for some background on HomePlug and G.hn would do well to peruse our first powerline networking kit review and our subsequent coverage of the tussle between HomePlug and G.hn.

The Comtrend PG-9172, like other powerline adapters, uses existing electrical wiring and powerline technology to connect devices at wired speeds without rewiring with Ethernet. Comtrend claims that the G.hn technology in the PG-9172 helps it deliver better real-world performance compared to HomePlug AV2 standards. It features MIMO (multiple-input, multiple-output) technology and supports encryption for secure communication.

The PG-9172 is available as a single adapter. Obviously, one needs a minimum of two adapters to create a powerline network, and our review kit came with two units. Each package has an adapter, a Cat5 Ethernet cable, and a brief installation guide.

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In order to support MIMO, the adapter makes use of the ground pin also. The rear side of the unit sports the HomeGrid certification logo. The bottom of the unit contains the RJ-45 port and a configuration reset button. The front side of the adapter contains LEDs to indicate power status, Ethernet link status and encryption status. Each adapter has dimensions of 93mm x 59.6mm x 35mm and weighs 100g.

The Comtrend PG-9172 is based on a Marvell platform. It uses the Marvell 88LX3142 for the G.hn digital baseband functionality and a Marvell 88LX2718 Analog Front End (AFE) chip. The platform features 128-bit AES encryption, and has a PHY rate of 1200 Mbps.

Using the adapter is a simple plug-and-play process. One plugged-in adapter is connected to the router / DHCP server, while the other adapter(s) can be connected to power outlets anywhere in the house. A maximum of 7 other adapters can be part of a G.hn powerline network, as per the specifications of the PG-9172. Most consumers can use the PG-9172 kits to extend their wired network in this manner without worrying about anything else.

Firmware upgrades are managed by the PG-9172 Upgrade Tool available for download on Comtrend's product page. Unfortunately, I never got the upgrade tool to work properly on any of the multiple machines I tried out. Consumers with technical awareness can also manage the adapters via a HTTP interface. This interface can be accessed by setting a static IP in the 10.10.1.0 subnet for the PC's network port connected to the PG-9172 unit. The adapter's web UI can then be accessed at 10.10.1.69 with the password 'paterna'.

The web configuration page provides essential statistics such as PHY rates. It also allows the user to enter a encryption passphrase. We find that power saving / inactivity detection mode is disabled by default. The firmware version can also be verified, and upgraded using FTP / TFTP. Unfortunately, direct upgrade of firmware via the web UI is not available. Advanced users can also configure multicast features, QoS and VLANs using the web UI.

Evaluation Setup and Testing Methodology

G.hn's claims of being better than HomePlug AV2 in real-world scenarios was always something we had wanted to test out for ourselves. In order to evaluate the claims, we took out all the powerline adapters that had come in for review over the last four years and subjected all of them to the same iperf benchmarks under the same conditions across different power outlets in a residence. Prior to going into the details of the evaluation, let us take a look at the features of the different powerline adapters being considered today.

Comparative PLC Configurations
Aspect	Comtrend PG-9172	ZyXEL PLA5405Netgear XAVB5501ZyXEL PLA5206D-Link DHP-541ZyXEL PLA5405ZyXEL PLA4205Comtrend PG-9172
Technology	G.hn	HomePlug AV2
Chipset	Marvell 88LX3142 for G.hn Digital Baseband Marvell 88LX2718 Analog Front End	Qualcomm Atheros QCA7500
Encryption	128-bit AES	128-bit AES
Performance	1200 Mbps (PHY) / 1000 Mbps	1000 Mbps (PHY) / 1033 Mbps (AV2 MIMO Powerline 0 - 65 MHz Theoretical Max.)
Miscellaneous Features	MIMO (Multiple Input Multiple Output) G.hn / HPAV Co-existence Technology	MIMO (Multiple Input Multiple Output)
Dimensions	93mm x 59.6mm x 35mm	90mm x 60mm x 27mm
Weight	100g	95g
Retail Availability	May 2015	December 2014
Current Street Price (Kit)	USD 77	USD 83

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All the testing was carried out in a 1800 sq. ft. single-level detached California residence built in the 1970s. The rough floorplan of the house, along with the testing locations, is presented below.

The evaluation of the adapters was done in an isolated network. A NUC with an Intel NIC (running Windows 10 Pro x64) was configured to act as a DHCP server, and placed at location 'M' (in red) in the above picture. The 'master node' powerline adapter was connected to it. Yet another NUC with an Intel NIC (running Windows 10 Pro x64) was connected to the other adapter in the network. The location of this NUC / adapter combination was varied for each adapter pair's evaluation run. We considered typical powerline adapter usage scenarios in deciding upon the locations for the testing (A - F in green in the picture above). All major rooms, including the garage, were covered.

The purpose of our benchmarking was not to tune the stream configuration for obtaining maximum possible bandwidth. Rather, we wanted to replay the same stream for multiple adapter sets in order to determine comparative performance. iperf with default parameters was used for benchmarking. On the 'server', we ran the following command:

TCP: iperf -s -B 10.1.1.2
UDP: iperf -s -u -B 10.1.1.2

The 'client' was connected to it using the following command:

TCP: iperf -c 10.1.1.2 -P ${num_parallel_streams} -t 30
UDP: iperf -c 10.1.1.2 -u -b ${curr_bw_to_test}m -t 30

The number of parallel streams were tested between 2⁰ and 2⁵ for the TCP case. The maximum obtained bandwidth was recorded. For the UDP case, we altered the bandwidth to test in order to arrive at the value that resulted in less than 1% packet loss during transmission. The roles of the server and client were then reversed, and the same benchmarks were processed.

HomePlug and G.hn Go Head to Head

This section presents the benchmark numbers obtained for the four different test cases outlined in the previous section. The Comtrend PG-9172 numbers are graphed in red, while the ZyXEL PLA5405 (representing HomePlug AV2 with MIMO support) numbers are in blue. The main tussle is between these two adapters - they are close in price (USD 77 vs. USD 83) and represent the best possible implementations of the two standards in the evaluated set.

Performance Metrics - TCP Downlink and Uplink

Node A represents the shortest physical distance between the tested nodes. This is a close fight between the HomePlug AV2 and G.hn adapters, with the PG-9172 coming out with a slight lead. Surprisingly, the ZyXEL PLA5206 SISO adapter is better than the PLA5405 in this scenario.

Node B is the garage outlet across the AFCI circuit breaker. The SISO adapter is the surprise winner here, though the G.hn PG-9172 comes a close second. The PLA5405 comes in third, quite a bit behind the G.hn adapter.

Node C is in the same wall as the garage outlet, and across the circuit breaker again. Here, the Comtrend adapter performs quite well, though it is really hard to choose between the HomePlug AV2 adapters and the G.hn adapter given the small differences in the bandwidth numbers.

Node D is one of the farther outlets from the master node, and the Comtrend PG-9172 adapter establishes a clear and sizable lead over the HPAV2 adapters.

Node E is in the adjacent room, and is one of the closer adapters (similar to Node A). The performance ordering is also similar.

The Comtrend PG-9172 emerges as the clear winner in Node F.

Performance Metrics - UDP Downlink and Uplink

The UDP results across all the nodes are similar in ordering to the TCP results.

 

 

 

 

 

The above results show that the Comtrend PG-9172 G.hn adapter has the best performance in almost all of the tested scenarios.

Miscellaneous Aspects - Power, Thermals and Coexistence

Powerline adapters tend to get quite warm under sustained loading conditions. The power consumption is also an interesting aspect, since these devices are kept on 24x7. We evaluated these aspects for the Comtrend PG-9172 and the ZyXEL PLA5405. While the master node was left as-is (with the DHCP server NUC connected) in the 'M' location in the floorplan, the other member of the adapter pair was connected to a Ubiquiti Networks mFi In-Wall outlet in the same room as Node C. The In-Wall outlet allows measurement of instantaneous power consumption.

A stress test was set up with iperf servers and clients running on the NUCs at either end. 16-stream TCP benchmarks were processed for 30 minutes from both sides simultaneously.

Under these sustained loading conditions, the G.hn pair was able to maintain 60 Mbps+ uplink and downlink, while the HPAV2 MIMO pair was able to maintain around 40 Mbps

At the end of the 30 minute stress test, thermal photographs of both units were taken using the FLIR One for Android thermal camera.

We find that the G.hn adapter ran hotter (more than 56C) compared to the HPAV2 adapter (around 50C)

The power consumption of the adapters was also recorded under different scenarios. Under stress, the HPAV2 adapter does consume more power than the G.hn adapter. However, the thermal design must be better in the former in order to maintain a lower case temperature. On the other hand, under idle conditions, the disabling of the power saving feature by default in the G.hn adapter results in much higher power consumption compared to the HPAV2 adapter.

PLC Adapter Power Consumption
Scenario	Comtrend PG-9172	ZyXEL PLA5405
Normal (No Traffic)	3.19 W	1.98 W
Stress Test (TCP)	3.85 W	3.97 W

Coexistence is important if G.hn adapters end up getting installed in apartments with pre-existing HomePlug networks. Marvell has been working on updating the firmware to improve coexistence. Even though our review units were not equipped with the latest coexistence firmware, we decided to test out whether HomePlug and G.hn networks could co-exist. Towards this, we created a HomePlug AV2 network to extend our primary network (192.168.1.0 subnet) and retained the G.hn network described above. The HPAV2 network's master node was connected to a power outlet in the wall adjacent to the G.hn master node.

Traffic in our primary HPAV2 network was restricted to a series of pings (over Wi-Fi to a PC connected to the second powerline adapter). In this scenario, we processed the stress test on the G.hn network. There is a clear loss of bandwidth, and the consistency exhibited in the previous run was no longer present. However, it did manage to stay above 35 Mbps all through. On the HPAV2 side, we lost around 4 packets out of a few thousand. On the whole, our conclusion regarding coexistence is that it works in our limited testing. Future firmware updates might help lessen the impact on the HPAV2 network while also enabling the G.hn network to have better performance consistency.

Concluding Remarks - What is Next for G.hn?

The Comtrend PG-9172 G.hn powerline adapter gave us the opportunity to look at G.hn technology in real-world scenarios. Our evaluation shows that the technology is quite competitive in terms of performance. It shows better resilience to noise and performs better than HomePlug AV2 products from late 2014 in almost all scenarios. In particular, AFCI circuit breakers don't seem to cause as much performance degradation in the PG-9172 as they cause in HomePlug adapters. All in all, the product delivers upon its claims and performs as expected. We hope to add some comparative numbers from the newer class of AV2000 HomePlug products in the near future.

Positives aside, Comtrend could definitely do with better default settings in the firmware (particularly for power efficiency). The firmware update process must be made more reliable. Better software QA wouldn't hurt. The HTTP interface should also be made more user-friendly with better capabilities.

It is great to finally see G.hn technology in retail. It might be painful in the short term due to initial coexistence issues, but, we can see that the G.hn side is taking a lot of effort to minimize the problems. HomePlug has a huge install base and still holds the lead, but, G.hn is no longer a vaporware competitor. That said, we would like to see more commitment to G.hn from Tier-1 vendors.

There is hardly any doubt that G.hn, considered standalone, provides a better user experience and has technical advantages. The issue has always been market acceptance and the existing install base of HomePlug demanding backwards compatibility in the pure powerline communication space.

The rising popularity of mobile devices has made Wi-Fi indispensable in the home network. However, wireless dead spots have been a major pain point for consumers. Most networking vendors have been trying to solve the wireless dead spot problem with a mixture of different products - Wi-Fi extenders, powerline adapters and other similar devices. Wi-Fi extenders usually don't deliver great user experience because the radio constantly switches between client and AP (access point) modes resulting in lowered effective bandwidth. A wired-to-Wi-Fi extender (using powerline technology) enables the extender to be in the AP mode 100% of the time, and in a different channel too. HomePlug built upon this strategy to become part of the Hy-Fi standard, aimed at making hybrid networking popular in the market. However, the Hy-Fi scheme has largely been given a cold shoulder by the market.

The HomeGrid forum and Marvell believe that the solution for a cost-effective and great user experience lies in the usage of G.hn as a backbone. The introduction of the ARRIS SURFboard RipCurrent series (a family of routers and extenders using G.hn technology) is indicative of G.hn's further push into retail channels. It is also an example of the hybrid networking idea as envisioned by the HomeGrid forum.

The announcement of the RipCurrent lineup also opens up the interoperability aspect of the Comtrend PG-9172. Given that both products are based off Marvell silicon, and both carry HomeGrid forum certifications, it shouldn't be an issue. Hopefully, our planned evaluation of the ARRIS SURFboard RipCurrent lineup will put any doubts to rest.

ARRIS is on board the G.hn train with their SURFboard RupCurrent lineup. It remains to be seen whether other Tier-1 vendors will join in. HomeGrid / G.hn seems to finally be on the right track and the momentum is now on their side. The HomePlug vs. HomeGrid tussle just got a lot more interesting.

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