Our new Wi-Fi SIP phone from Linksys arrived few weeks ago and we have included it in our various tests to see how it works. The model is the WIP 300, first product of the portfolio and a cheap product, very far from a design and material point of view from industry standard in traditional enterprise voice, but it is targeting another audience and we see some interest in it.

Since the Wi-Fi radio system is today really simple to be installed, adding an IP mobile phone to our VoIP system became an easy task, a simple access point plugged on the network is enough to start with.

First approach

Quality is average but no surprise with a US$110 product that should include a SIP stack and Wi-Fi connectivity. With 90 grams it is surprising and conformable when used. The phone is shipped with an external power supply using a USB connector, we can also power it with an external cable directly on a computer, easy and simple¹.

Talking about autonomy, it is not really serious compared to a DECT phone or even a GSM. It is true that Wi-Fi is stressful for batteries, but user should not be impacted by this. We have measured around 24 hours autonomy (with screen off) and one hour in communication. This phone should not therefor be the main phone but can really be a good partner for a fixed phone in order to go to a conference room or moving in the building.

It is lacking a cradle to install the phone when not used and power it through the USB port, but nothing really important.

Configuration

Wi-Fi and IP configuration of this IP phone are really simple. Our lab installation is really basic and looks like most SOHO installation: one access point connected directly on the internal LAN and protected by a long enough WPA pre-shared key. Other security options are available from no ciphering to WPA enterprise with PEAP and WEP².

Once the Wi-Fi is associated to the mobile network, our DHCP server has provided the phone with an IP address, it is now possible to configure it through the web interface or continue with the embedded one.

The SIP part is well organised, but an association between the SIP context and the network profile is required which is not straighforward. We can prepare multiple SIP environments, but only one registration can be performed at a time and only one Wi-Fi configuration can be prepared, mobility between various installations it not possible. On each SIP profile, we can specify the registrar, some delays and the codec, but only G.711 A law, G.711 u law or G.729A. We would have prefered to G.729A another adaptative codec free of charge, but the product is clearly targeting internal LAN installation, G.711 is perfect in that case.

The phone itself can be configured for screen background image, ringing sounds or internal diary. Even a mail client is present but we haven’t tested it; what is the intent of this one?

30 seconds are necessary from power up time before being registered onto the network and can accept or place a call. This is comparable to some cell phone but why not using something permanent like on PDA?

Usage

Once configured and registered on our Asterisk test server, the screen is indicating valuable information through pictograms (connection status, battery level, Wi-Fi signal, …). The Wi-Fi SSID and SIP name are also printed on the screen, good points. The power indicator is clear but not accurate at all, you loose power before any alert. There is also a Wi-Fi signal level, easy to read and understand, should be good for many users.

Receiving or giving a call is very easy and works well. If you activate screen shutdown for power saving, you better have to reactivate the phone before dialing, we have encountered some voice quality issue when dialing too fast.
Sound quality with a G.711 codec is good for a mobile phone, better than GSM , no surprise. The communication delay is relatively high as reported by the Asterisk qualification process, around 150ms on our local network, but no real impact on the voice itself.

For some test calls we gather statistics that are really in line with expectations. Test lab was using a 100Mbps network, Asterisk 1.4.4 on Debian and all IP phones and test systems on the same broadcast domain, G.711 A law for the codec:

call lenght	call setup (ms)	jitter3 (min/avg/max)	loss %	Wi-Fi
25 s	2	16/32/48	0	near AP
61 s	3	22/36/64	0	near AP
1m31s	3	2/28/52	0	near AP
2m01s	1	1/32/74	0	-15dB
2m59s	1	1/33/150	0	-20dB
2m06s	1	1/38/69	0	-20dB
1m10s	1	1/37/65	0	moving

Some pure SIP tests demonstrate the SIP stack stability, no surprise for a Linksys product.

Management

This point is not the good one on this product. The configuration through the web interface is not proposing the same parameters as on the phone itself, why? No available log in order to know why the phone is not registered, the test tools are only available on the phone, why not in addition to the web interface?

We have tried an automatic installation through HTTP but even if the file is uploaded well at boot, an error is present in this one and it was impossible to accomplish the configuration. We are really far from a Polycom installation, but we will retry in the future…

In a nutshell

Strengh

• good price/quality ratio
• low infrastructure cost to add mobility for a VoIP network
• easy to configure
• Wi-Fi security supporting WPA in pre-shared key and enterprise
• strong SIP stack

Weakness

• low power autonomy, battery indicator not accurate
• Wi-Fi as a mobility media is not good, this is not really an issue of the product but such solution cannot be applied to a complete mobility requirement in the enterprise, see also “Voice over IP and Wi-Fi?“
• low diagnostic tools and log
• limited set of codecs
• fragile product⁴
• firmware upgrade requires IE, not working with Firefox, why?
• we encountered some reboot during tetsts, mainly due to power supply we assume.
• a cradle would be great, even as an option
• INFO message for voice mail notification doesn’t seems to work.

Conclusion

In order to add some mobility on your voice over IP network, this is a really good option compared to DECT which is too expansive for 2 to 5 mobiles on a big office.

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1. the cable is not available with the phone, bad point [↩]
2. still existing ? [↩]
3. via RTCP [↩]
4. don’t let it fall down [↩]