Data transfer via WLAN while Bluetooth device scanning

[jawadakhtar]

Hi,

I am facing problem with WLAN connection while scanning for Bluetooth devices. The data transfer of WLAN paused when the application starts scanning for bluetooth devices. We need to scan bluetooth devices form time to time. Therefore in this scenario the WLAN data transfer is paused remaining the connection remains Active, but with no data transfer. After a time when the scanning completes the data transfer again started. According to our scenario, we need to scan bluetooth devices from time to time, and therefore this is causing the problem.

Any suggestions and ideas why this is happening and how it can be fixed.

Thanks,

Jawad.

[wizard_hu_]

Do you have any User::WaitForRequest calls in your code (especially in the BT-discovery part)? If yes, they are the most probable cause.

[jawadakhtar]

No, I checked the code and there is no call to User::WaitForRequest. Here is the code for device discovery. The problem is only with the discovery process because once we have successful connection with the pair device the data transfer has no issues.

class MBtDiscovery
{
public :
virtual void DeviceServiceDiscoveryCompleted() = 0;
virtual void DevicesDiscoveryCompleted() = 0;
virtual void DeviceDiscovered(TDeviceData& aDeviceFound) = 0;
virtual void ErrorServiceDiscovery(TInt aError) = 0;
};

//CLogFile is for logging
//aDeviceName is for BT device name we need to scan for connection
void CBlueDiscoverer:iscoverL(const THostName *aDeviceName, MBtDiscovery* aDiscoveryCallback, CLogFile* aLogger)
{
if (IsActive())
return;

iDeviceName.Zero();
iDiscoveryCallback = aDiscoveryCallback;
iLogger = aLogger;

if (aDeviceName != NULL)
iDeviceName.Copy(*aDeviceName);

//RArray to contain all searched devices
iDevicesList.Reset();

//find protocol
TProtocolDesc pd;
TProtocolName pname;
pname.Copy(_L("BTLinkManager"));
User::LeaveIfError(iSockServ.FindProtocol(pname, pd));

//open to resolve host
TInt err = iHResolver.Open(iSockServ, pd.iAddrFamily, pd.iProtocol);

if (err != KErrNone)
{
if (iLogger)
iLogger->Log(_L("Error occured. Error : ") , err);
}

iAddr.SetIAC(KGIAC); //KLIAC is not configured on connectblue
iAddr.SetAction(KHostResInquiry|KHostResName|KHostResIgnoreCache);

iStatus = KRequestPending;
//RHostResolver
iHResolver.GetByAddress(iAddr, iEntry, iStatus);

SetActive();

}


void CBlueDiscoverer::RunL()
{
AsyncRequestProcessor(iStatus);
}


void CBlueDiscoverer::AsyncRequestProcessor(TRequestStatus aStatus)
{
if (iStatus == KErrNone )
{

if (iLogger)
iLogger->Log(_L("Bluetooth device found."));

//cast the socket address to Blue Tooth address
TInquirySockAddr& sa = TInquirySockAddr::Cast( iEntry().iAddr );

TDeviceData devData;
devData.iDeviceName = iEntry().iName;
devData.iDeviceAddr = sa.BTAddr();
devData.iDeviceServicePort[0] = sa.Port();
iDevicesList.Insert(devData, 0);

if (iDiscoveryCallback)
{
iDiscoveryCallback->DeviceDiscovered(devData);
}

if(iDeviceName.Length() > 0)
{
if (iDeviceName.Find(iEntry().iName) != KErrNotFound)
{
if (iDiscoveryCallback)
iDiscoveryCallback->DevicesDiscoveryCompleted();
}
else //not found, we need to query next device
{
if (iLogger)
iLogger->Log(_L("Query next available device ..."));

//RHostResolver
iHResolver.Next(iEntry, iStatus);
SetActive();
}
}
else
{

if (iLogger)
iLogger->Log(_L("Query next available device ..."));

//RHostResolver
iHResolver.Next(iEntry, iStatus);
SetActive();

}


}
else if (iStatus == KErrHostResNoMoreResults)
{
if (iDiscoveryCallback)
iDiscoveryCallback->DevicesDiscoveryCompleted();
}
}

[wizard_hu_]

Yes, it seems to be harmless.
For testing if it is some kind of platform/hardware restriction, you can try using completely independent applications (like downloading something in the browser and doing BT discovery).

[laa-laa]

Speculating a little bit: It may be a deliberate feature.

Both WLAN and Bluetooth operate on the same 2.4GHz ISM band. The protocols are designed to coexist nicely and handle collisions etc. gracefully. Bluetooth device discovery works basically by going through the frequency range, sending "anyone here?" inquiry packets and listening for replies from discoverable devices. To make the discovery process more reliable it makes sense to silence some unrelated activity on the frequency band. It could also be a resource issue that the specs simply don't allow Bluetooth inquiry to coexist with WLAN in the same device. (Cannot remember the exact time-slotting schemes for Bluetooth inquiry and I'm too lazy to check.)

Lauri

[wizard_hu_]

Yes, that is all true, however it may still worth a try, especially since Jawadakhtar already has an application doing WLAN transfer (tracking that one may be easier than checking with the browser), so basically the test could be a simple switch to the BT application and initiating a search (for pairing for example).