Teardown: Wireless network extender adds differentiating features

Article By : Brian Dipert

The developers of devices based on mature technologies are quite creative at finding ways to continue to innovate and differentiate their products.

I’ll begin this teardown with an admission: generally speaking, I’m not a big fan of wireless network extenders, though I’ve used them in the past. This pessimism is because they are bandwidth, latency, and available-channel-usage constrainers, due to their fundamental design. Imagine a wireless client device like a laptop, on the edge of the expanded network footprint. It sends a packet to the network extender, which turns around and rebroadcasts it to the router at the network’s nexus. The router sends a packet back, which the network extender receives and rebroadcasts to the laptop. Rinse and repeat.

Contrast this with a wireless access point, whose “backhaul” to the router at least leverages high-bandwidth, low-latency wired Ethernet (or other copper-based cabling … powerline, MoCA, etc.). But that being said, keep in mind that the fundamental point of a network extender is for use in situations when network cabling isn’t available. And performance constraints (and spectrum clutter) aside, isn’t a slower wireless signal (generally) better than no signal at all?

In a recent teardown, I pointed out that ongoing networking innovation has steadily produced ever-smaller devices with cooler and much less power hungry operation, while simultaneously delivering ever more bandwidth, range, and feature capabilities. Whereas IEEE 802.11ac (aka “Wi-Fi 5”) is today’s mainstream technology generation, with 802.11ax (Wi-Fi 6) queued up right behind it, the ASUS RP-N54 we’ll be looking at today (which I picked up from Newegg last summer for $4.99 on promotion and after rebate) is based on prior-generation dual-band 802.11n.

But … there’s plenty of existing 802.11n (and earlier)-based hardware already deployed in the field, for which gear intended for network upgrades is still relevant to the associated potential customer base. Consider, too, that 802.11n is quite mature at this point, translating into low bill-of-materials costs for system suppliers that still want to play in this particular space. And predictably, as per my comments on Bluetooth audio adapters a while back, the developers at those suppliers are quite creative at finding ways to continue to innovate and differentiate their products both from their own prior-generation offerings and from those of competitors. To wit, I’ll point out the unique attributes of the RP-N54 in the following sections.

First off, however, some as-usual unboxing shots:

Asus RP-N54 package

Here’s one of those added differentiating features … tap on the front of the unit, and a white LED turns on, pointing down from the bottom of the unit. Nice for when, for example, you want to briefly illuminate a hallway path with the network extender plugged into an outlet on its wall:

Asus RP-N54 package

Here’s another enhancement: you can stream music to it from an ASUS-branded app for Android or iOS, akin to the AirTunes receiver feature supported by Apple’s now-deprecated Airport routers and access points. Also note that the family of devices listed also includes not only an entry-level single-band (2.4 GHz) unit but also a higher-end dual-band 802.11ac variant:

Asus RP-N54 package

Missing UPC code reflective of rebate application:

Asus RP-N54 package

Asus RP-N54 package

Digging in … after slipping off the outer packaging sleeve, the first thing you’ll encounter is the documentation stack, which IMHO is really smart on ASUS’ part:

Asus RP-N54 documentation

On top is a dual-language quick-start guide:

Asus RP-N54 quick start guide

As I’ve noted plenty of times before, high-volume consumer electronics devices like this make their money on cumulative profit margin, not high per-unit profit margin. The scant per-unit margin can quickly evaporate if the consumer reaches out to customer support, and turns negative if the consumer gives up and returns the device to the retailer, thereby explaining the prominence of the quick-start guide and, directly below it, a notice (double-sided, formatted slightly differently per-side, but in English in both cases … maybe mine was a misprint?) pleading for the consumer to call ASUS first instead of immediately initiating a return. Also included are warranty and FCC pamphlets.

And we’re finally in business. There’s literally nothing else in the box … no Ethernet cable, no more paperwork, etc:

Asus RP-N54

Asus RP-N54 plug

Remove the airflow-restricting transparent plastic protective sheet and our dissection victim comes into full view, complete with status LED sets for both 802.11n bands along the bottom (“5G” stands for 5 GHz, by the way, not the new cellular standard):

Asus RP-N54 network extender

Asus RP-N54 network extender plug

Along the left side are, left to right, the Wi-Fi Protected Setup configuration button, a power switch, a recessed reset switch, and (speaking of airflow) a passive thermal transfer vent:

Asus RP-N54 vents

Along the right side are the analog audio output for the media streaming receiver support, an Ethernet connector (which I’ll talk about more later), and another airflow vent:

Asus RP-N54 ethernet connector

And here’s the underside, complete with more airflow vents and, at bottom, the aforementioned downward-pointing illumination LED:

Asus RP-N54 LED

Time to crack open the case. Pressing on the underside sticker revealed an indentation suggestive of a recessed screw head, a prognostication which ended up being spot-on. Add a flat-head screwdriver to the mix, to release the various retaining tabs around the chassis, and we’re inside:

Asus RP-N54 case

Here’s the underside of the front panel. Note the exposed section of copper. It corresponds to the bottom-left location of a switch in the bottom left of one side of the PCB. Press on the front panel, the switch makes contact, and the downward-facing LED (which you’ll see shortly) illuminates:

Asus RP-N54 contact plate

Also notably evident are the row of LEDs at the bottom and the 2×2:2 MIMO 2.4 GHz and 5 GHz antenna arrays along either side, at the top:

Asus RPN54 PCB front

Here’s another perspective:

Asus RP-N54 antenna

Remove one more screw, and the PCB lifts out of the chassis:

Asus RP-N54 connected PCB

The power cable connector detaches with ease; just look at that heat sink!

Asus RP-N54 heat sink

It corresponds to the mysterious grey rectangular region in the upper left of this side of the PCB, below which, I’m guessing, is the system SoC, along with another mysterious grey rectangular region (this time square) next to it:

Asus RP-N54 PCB

What are they? Well, let’s step back a bit. I wasn’t able to find much info on the ASUS RP-N54 online, but I did find more documentation on its sibling, the RP-N53 (here, for example is the OpenWRT open-source firmware page). A really odd thing … the RP-N54 doesn’t even have a FCC database entry (here’s the FCC certification info on the RP-N53)! And the descriptions (not to mention the appearances) of the two devices on the associated ASUS website product pages are pretty much identical. The only differences you’ll see come from perusals of the Amazon pages for the RP-N53 and RP-N54, wherein the latter seemingly has supplemented the foundation network extender (aka “wireless repeater”) functionality with added wireless access point support (thereby explaining the wired Ethernet port’s presence … on that note, I’m surprised the RP-N54 doesn’t also have wireless network bridge capabilities like those on the ASUS EA-N66 I dissected a while ago).

My working theory after doing this initial research was that from a hardware perspective the two devices were identical, differentiated solely by expanded software-based capabilities on the RP-N54. And, as I’ve mentioned before, I strive whenever possible with these teardowns to return the devices to fully operational status afterwards, followed by donation visits to Goodwill. So I visited the WikiDevi page for the RP-N53 to see what ICs were inside it … and in the process got confirmation that my theory was correct.

“1244-01000902-50Z” is silkscreened on the main board in the FCC photos.

That’s also, as you can see from my photos, the ID silkscreened on the main board of the RP-N54. Same hardware! So WikiDevi’s IC info for the RP-N53 applies equally. One chip, handling system processing along with the 2.4 GHz wireless subsystem, is MediaTek’s MT7620A. The other, doing 5 GHz Wi-Fi duties, is Ralink’s (now MediaTek’s) RT5592.

read more teardowns

In-between them is a Macronix MX25L6406E (PDF) 64 Mbit serial interface NOR flash memory, presumably housing system firmware. And below the mysterious grey rectangular region is a DRAM, specifically a Winbond W9751G6KB-25 (PDF) 512 Mbit DDR2 SDRAM. Other notable elements of this side of the PCB are the LED array at the bottom, which handles the aforementioned downward-directed illumination duties, and the DAC and amplifier associated with the analog audio output connection in the bottom left corner.

I’m happy to say that once I reconnected power, put the PCB back in place and reassembled the enclosure, the RP-N54 worked as good as new. Off to Goodwill I go (had the RP-N54 supported wireless bridge capabilities, I might have kept it); it’s now time for your comments!

Brian Dipert is Editor-in-Chief of the Embedded Vision Alliance, and a Senior Analyst at BDTI and Editor-in-Chief of InsideDSP, the company’s online newsletter.

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