Comment 62 for bug 1670041

Using this guide https://www.dell.com/support/article/ng/en/ngdhs1/sln306440/killer-n1535-wireless-firmware-manual-update-guide-for-ubuntu-systems?lang=en and upgrading to latest firmware for Dell XPS 15 on Ubuntu 17.10 for the following below solved my wifi frequent connection drop while NetworkManager was still showing the Wifi was connected.

uname -r
4.13.0-16-lowlatency

dpkg -l linux-firmware | grep ii
ii linux-firmware 1.169 all Firmware for Linux kernel drivers

lspci -vvv
02:00.0 Network controller: Qualcomm Atheros QCA6174 802.11ac Wireless Network Adapter (rev 32)
 Subsystem: Bigfoot Networks, Inc. QCA6174 802.11ac Wireless Network Adapter
 Control: I/O- Mem+ BusMaster+ SpecCycle- MemWINV- VGASnoop- ParErr- Stepping- SERR- FastB2B- DisINTx+
 Status: Cap+ 66MHz- UDF- FastB2B- ParErr- DEVSEL=fast >TAbort- <TAbort- <MAbort- >SERR- <PERR- INTx-
 Latency: 0
 Interrupt: pin A routed to IRQ 140
 Region 0: Memory at ed200000 (64-bit, non-prefetchable) [size=2M]
 Capabilities: <access denied>
 Kernel driver in use: ath10k_pci
 Kernel modules: ath10k_pci